Although we see the subheadline
Watch live on MLB.TV or listen live as likely Opening Day starter Aaron Nola takes the hill tonight
upon checking, we see that the game is not on TV from Washington. Evidently the bush league team in Washington is not televising the game and this season, only the home team does TV and the visiting team will use that feed with their own not in the ballpark announcers.
Looks like there is a radio feed from the Nationals but of course, no Phillies broadcasters giving us the action for this game. There is a Gameday preview page so it looks like they plan to have Gameday for the exhibition game in Washington tonight. I expect it will be the spring training type Gameday where they really only show results, not pitch by pitch play. I sure hope that once they start the "season" next weekend, they will have real Gameday operational.