Universal pays to use the IPs that are not owned by Comcast. Thus, the rumor I heard regarding Scream. Namely, that Universal approved, designed, and built Scream under the assumption they could get the rights. I know the assumption is that Dimension pulled out last minute, but (and I'll admit it's a rumor a couple degrees separated) but I'm inclined to believe they weren't at the table in the first place.
Its the fact that, yes, Universal pays for IPs that actually makes this more believable. If Dimension had the money in pocket, I can't imagine they would back out. They would absolutely back out if they took offense to Universal's gross assumption.
EDIT - And this is the rumor I mentioned earlier in the summer.