This would likely not cross into anti-trust territory. Besides, they have tried it before... http://money.cnn.com/2004/02/11/news/companies/comcast_disney/ Large cable companies are running out of small mom & pop providers to buy, and have amassed huge cash reserves, which they would like to find something to do with, one of which is to buy a large content provider, or possibly (though they keep denying the rumors), buy a wireless provider. Most of the wireless providers in the U.S. are too large to be taken over by even the largest cable companies, though.

Additionally, many MDUs bundle basic cable service with tenant's rent; these bulk agreements with the cable companies are often priced well under advertised rates (often less than half what one would pay outside of the agreement). If these contracts are not allowed for many larger apartment complexes, the rates that the tenants pay would go up drastically, not down (at least from the company that has ownership of the infrastructure in the building).