Thank you for posting this.
We, also, are from the Boston area and are booked on Maasdam for June to do Boston to Montreal but we are staying aboard and doing back-to-backs for the return sail back to Boston. A part of the consideration to do the b-to-b's was transportation back to Boston although it was not a big factor. We very often stay aboard for two cruises.
We did Maasdam last July when it was a return trip Boston to Boston. That was fabulous and we loved the cruise.
However, because it was a roundtrip, there was not enough time to go to Montreal. We're looking forward to seeing Montreal again as it has been a while since we were there and are so happy we will have two full days In Quebec as we will be there both going and coming.
I will surely keep in mind about the bus for a possible future Canada/New England cruise.
Hope you have a great time.