No only busses that are planned as replacement for trains or busses that are part of it (see benefit portal of Interrail). 

A bus ticket bought there on the spot-there might even be the odd comp. which does not advertise at all on www (an extreme utter surprise for fone-adapts) and the price will be much less as an average pass-day would cost you. It will also be less as half the time the train would need.