Buba mentioned the Ottomans being more likely side with the Entente in this scenario.
I think almost the *only* way the Entente can win in this scenario is the Entente can have the good fortune to not do worse in 1914 (perhaps by taking fewer losses in opening Lorraine offensives) and *then* having the Ottomans join in on the Entente side as a counter-balance against the Italians being on the other side. If the Ottomans are still on the CP side, along with the Italians, in my view, the advantage tilts even more to the CP.
So here is a quick and dirty scenario I worked out where World War One in western, northern, central, and Eastern Europe ended up with similar results to OTL, an ultimate pyrrhic Entente victory, but with details changing in Southern Europe, the Mediterranean, and Middle East, because the Italians and Ottomans are on opposite sides from OTL. Enjoy:
The Italians join the CP from the beginning. But the British grant the Ottomans their dreadnoughts. The Entente also diplomatically do a full court press on the Ottomans. Meanwhile, the Goeben and Breslau, if not sunk en route, reach safe harbor in an Italian or Austrian port before reaching the Ottoman Empire to reinforce German diplomacy with the Turks.
The Entente, especially France, and more grudgingly Russia, decides its important to bid for Ottoman support when the French front is up in the air. They offer the Ottomans straightaway the restoration of the territories the Italians conquered and occupied in the 1911-1912 war, Libya/Tripolitania and the Dodecanese.
The Ottomans like the sound of that. But they bargain harder. The Entente can't offer back territories lost in the the 1st Balkan War because the Balkan neighbors of Turkey are presently neutral and they don't want to put large Christian populations under them. Likewise, Russia won't be offering Kars-Ardahan, and Britain won't be offering Cyprus or Egypt, France won't be offering Tunis.
However, they can yield their capitulations and special economic rights, and by declaring war on the CP, the Ottomans can unilaterally seize CP properties and revoke their capitulations. The Ottomans can also demand more territory at enemy expense, and the Entente can oblige them by promising them the Italian colonies in East Africa, Eritrea and Somalia, provided the Ottomans provide troops to take and occupy them. Handing over African Muslims to the Ottomans is not seen as problematic as handing over Balkan Christians, or Muslim subjects of Paris, London, or St. Pete.
At most, such promises of Italian loot slightly complicate relations with Abyssinia. The Entente could consider compensating Abyssinia by compensating her with a small Eritrean coastal strip or port.
This adds up to convincing Talaat and Djemal to overrule Enver and declare for the Entente.
In the mid-term, with more Italians in the west, the Germans can send the Austrians a little more help in the east earlier. Przemysl never falls and is relieved. The anti-Serb campaign doesn't go any better than OTL for Austria.
The Austro-German offensive throwing back the Russians in Poland and Galicia happen a little earlier than OTL, with more Germans participating than OTL, although more Russians can participate on the other side, not having an Ottoman front. Relieved on that front, the Austro-Hungarians can take down the Serbs in fall 1915 while the Italians take down the Montenegrins and occupy Albania, even while getting stalemated in the Alps (vs. France, not Austria), and slowly getting ground back in their African territories under Ottoman, French, and British pressure.
The Serbs do no escaping to the west in this TL, but instead to the south to Salonika. With an Entente Ottomans providing an Entente base in Thrace, the Bulgarians dare not declare for the CP, despite the temptation of Macedonia. The probable meeting of western Entente occupying forces and retreating Serbs in Salonika after a slow fighting retreat through Macedonia likely reinforces this deterrence.
While securing the straits for Entente use in shipping (and saving the opportunity cost, especially from winter 1914-1915 and beyond by sparing the British and Russian Empires from anti-Ottoman campaigns and troop commitments, Ottoman-Entente ties, and suspected and open secret about the retrocession of the Dodecanese means active pro-Entente sentiment is squelched in Greece. [Possible alternative, no Entente landing in Salonika, and Serbs are interned]
The takedown of Serbia relieves Austria-Hungary's situation alot.
Not sure what happens in Romania.
But 1915 and 1916 and 1917, the Russians have more men for the front, they also have more export earnings, and are importing more locomotives, so they are matching increased Austrian strength on their mutual front.
In 1915 and especially 1916 and 1917, the British Empire has many more troops in France, having pretty much settled colonial front in the Pacific and Africa, including Italian possessions, and possibly even taken Sardinia or Sicily. (though that's doubtful, and would be a dead-end manpower suck for GB and Italy both)
By 1916 or so, naval attrition of CP, Triple Alliance fleets and effectiveness of blockade has matched OTL levels, so Germany is doing USW.
Results in 1917 - US entry, Russia breaking under strain and revolutions and quitting, then 1918, CP capitulating, end up in a wash, matching OTL.
Maybe Italians loses Valle D'Aosta to French occupation like the Saar. Treaty for Germany is identical to OTL. Trianon for Hungary is basically identical (especially assuming Romania enters and there is an eventual Salonika front), but Bulgaria is status quo ante - so no Neuilly and it keeps its Med coast, and no Sevres for Turkey because it's a winner. St. German for Austria is nearly identical to OTL, except that the Italo-Austrian Republic border is on ethnographic lines, and possibly as the Habsburgs and Italians set it, with German -speaking Sudtirol staying with the Austrian republic (no need to reward Italy as an enemy power). Italy loses its colonies to the Ottomans which become LoN "."Mandates" of the Ottoman Empire, that it treats in most cases as sovereign territory.
As a consequence of the Russian collapse and Civil War, the Ottoman Empire also occupies Kars-Ardahan.