Browsing through megabus.com's web site today reveals that they are apparently coordinating operations with Eastern Travel, one of the larger "Chinatown" operators on service between NYC and Balto. & DC. Notes on the schedules advise riders that some megabus runs are operated by Eastern and that they should look for Eastern's white & red buses.
Megabus.com's bus stop maps also show Eastern's even though they may be in different locations. In Balto. megabus stops at White Marsh while Eastern stops at the Cherry Hill LR stop. The DC and NYC stops are in walking distance of each other.
Neither company's timetables identify which is operating what trips or if they are selling each others tickets.
According to today's Baltimore Sun, CoachUSA, owner of megabus.com, acquired Eastern Travel in December 2008.
Further research reveals the following from the new April 2009 issue of "Bus Ride" magazine, where CoachUSA is merging Eastern and Today's Bus to form "Dragonbus.com"!
http://www.busride.com/article.asp?IndexID=1214
Heh. Stagecoach vs. First.