Angelos "claimed" that he one's DC. But my understanding is tha the TV territories are assigned by MLB in the franchise agreement between MLB and a team, in this case, the Orioles. I believe that the territories are subject to change and they do change. When MLB expanded into Florida with the Marlins, then the Rays, that was Braves territory. MLB adjusted the territories for the Marlins, then split it again for the Devil Rays.
Additionally, a team only has exclusive rights to the city/county it is located in (Baltimore County) and the cities/counties that it touches. So, since Baltimore does not touch PG, Montgomery Counties, DC, Northern Vieginia, to, Angelos should not have had a "right" to those TV territories.
Furthermore, this opens MLB to lawsuit next time a team relocates or if MLB has another round of expansion and it has to "take away" some team's TV territory and they object on the MASN precedent.
But hey, that's just my 2 cents.