National TV Network Coverage- Rest of Season

Does anyone know about how etched in stone the rest of the National Television schedule is for the Celtics? My concern is, if the networks have the same ability as the networks that cover football to flex game times and change games covered all together like NBC does for the last 1/4 of the season. If the Celtics team funk lasts much longer, I would look for TNT, ESPN & ABC to drop previously scheduled games from national coverage. We all know that NBC was very unkind for Celtic coverage in the mid-late 90's. I'm thinking the networks will take that action if they have the freedom to do so.