Two problems.

1. If they did, they would not get to claim infringement with other infringers (no outright ownership of the patents), some of the other infringers could be competitors (and how much corporate advantage would have to be given up if your competition hasn't, but still can, license from EDIG as it is now?)

2. They would not get access to the patents that were "cross-licensed" in the settlements, again, some could be competitor's patents.

It's possible they could too make up some of the billion dollar cost by paying off DM and using their own in-house to go after the remaining infringers.