Kim,
I've been looking for answers about delay in initiating BCG treatment, but can't come across anything. I'm pretty sure that Wendy would have an idea about the risks of delay.
To be honest, I wish that the Doctor had given the Mitomycin C. (But then, I don't think you need to be riled up any more than you are against this Uro.) Surely, though, on the positive side, how do you know that this Doctor won't turn out to be right?
I agree that the treatments should be put off until you get the MRI results. Like my Doctor told me, there are 6,000 different things that can occur in response to BCG's. You don't want to muddy up the picture in diagnosis of any other medical issues.
Good luck and I hope someone comes up with an answer to your question concerning delay of treatment.
Your friend,
Rosemary