Well the Blacklight Virus should be "relatively" easily containable as conventional forces were able to contain it on Manhattan thanks to the issues it had with crossing large bodies of water. I'm not sure if the water thing would help here but Holy Terra having lots of fortresses should help with containment just as well. And I'm assuming the Imperium of Man has forces more capable than conventional 20th Century modern militaries does in regards to eradication. So that at the very least should be a win for the Imperium. So a win IMHO.
As stated earlier, the Necromorph outbreak depends on the number of Markers though unless the Imperium really drops the ball, I see this as mostly a spectrum of victory to draw for Holy Terra depending on how much of the planet is devastated prior to quarantine and eradication. I don't think any of the general Necromorph forms are too much of a threat militarily to the overwhelming force that can be brought to bear on them by the Imperium of Man. So probable win, highly likely draw at worst.
Thing would be a challenge since it's an intelligent alien. Once it's found it can be eradicated, but they'd have to detect it. If they can use Psykers or the like it might actually be very easy. Plus we have no idea how prolific it can spread. Maybe it's almost a no limits fallacy if it gets to a jungle or even a grassland, who knows. But with that as an unknown, I'd give odds to the Imperium figuring out this one and excising it before it gets out of hand. So I'd say a Highly Probable win here.
The Beast is a tricky one. It's never been shown how it behaves on the surface of a planet. It can infect organic matter as quickly as it can almost every starship that exists in Homeworld and it can do so very rapidly. It also possesses an incredible cunning. Assuming that it can affect planetary surfaces (or else why bother having it in this scenario) the only way to destroy it I would assume would be nuking it from orbit before it spreads too quickly... especially if it infects any spacefaring vessels. Or else it might just as well be ggwp for Holy Terra and much of the galaxy.
Which would count as a loss.
Detecting the Beast could happen pretty quickly, as would reporting its danger, so like with the others, it probably could be eradicated before its too late.