Direct TV will add chanels from other states to their home service for a fee. Will Comcast do this? Specifically, looking for WETA, Wash DC and WMPT, Maryland.
Comcast does not offer that. Satellite services may be allowed to do that since they already carry the signal through the satellites and may not be subject to DMA (Designated Market Area) laws. Comcast cannot really do that as it would mean having to make room available in the already shrinking TV bandwidth, along with being required to follow DMA laws.
(DMA means that they cannot carry an out-of-market channel unless a 'competing' channel agrees with it. You can see posts about channels being dropped recently due to local channels complaining about Comcast carrying a competing channel.