I don't see what the problem is, really. XM & Sirius should be bending over backwards to make their union pass muster for regulators and legislators. Similar concessions were made when Dish Network and DirecTV made similar acquisitions, putting helping start up channels like LinkTV, Free Speech TV, BYU-TV and COLOURS gain significant clearance.
As a publicly-traded company following licensing by the FCC, XM-Sirius setting aside a few channels for minority interests and for the public interest at large seems very reasonable. Such channels would not put a burden on the combined company itself.