Hello... As Cynthia said, a partial hasn't traditionally been used for transitional cell carcinoma (TCC), but perhaps in your husband's case, the doctor is thinking that if he can remove the area where the T2 invasive tumor was found with clean margins, then with regular monitoring, he can take care of any future recurrences before they progress past the Ta or T1 stage.
It seems doctors are leaning more toward bladder preservation if possible, so that sounds like the approach Dr. Baracus is taking. The tumor site being in the dome is the area that allows the partial to be done. Just ensure you have a very candid discussion of how he would handle any future tumors because TCC does have a pretty high probability of recurrence.
As far as my own partial cystectomy, I cannot tell any difference now as far as bladder capacity than before the surgery. My tumor site was fairly small, so the resected wall was probably likewise.
Best of luck as the two of you move forward with his treatment. Please keep us posted as to how he is doing. I will be happy to answer any questions you may have about my own surgery experience.