Cher,
Good for you! That's the right attitude. Most likely, they will call for an abdominal CT scan and chest xray first. If they already see things with that, they may just start treatment. If they don't see anything on that, then you should push harder for the CT/PET scan. That's head to toe and they superimpose the CT image with the PET scan. I think they don't go straight to CT/PET because of the expense.
My local uro ordered them in that order when I had a recurrence. Nothing could be seen in my case (even with a cysto) but the cytology (urine test) came back positive for high grade cancer cells. Thankfully, nothing showed on any of them and I was simply able to get my bladder and prostate removed and the cancer has remained gone since. Mine was only T2 though and it was barely T2.
Most likely, your husband is going to require some form of chemo even if they don't find anything in the scans as T4 increases the chance that it can get elsewhere. It depends on the doctor, as some like to do the chemo before and others like to do it after the radical cystectomy. Given that it has spread (as long as it's not spread other places) to the prostate, its highly likely that he's going to need a radical cystoprostatectomy (removal of bladder and prostate).
I hope you are OK with me telling you this kind of stuff. My style is to be pretty up front with likely scenarios as it is usually better to be prepared and have an understanding of probable next steps so you know what to study up on.
You may want to start posting any follow up questions in the "Invasive" section of the forum and also reading up on some of the posts there.
When you are reading, you may find some people calling T4 metastatic. It is not. T4 is spread to the surrounding areas. Metastatic is sometimes called distant spread and it is indicated by lymph node, lung, bones, or brain involvement.
We're all hoping it isn't metastatic and at this point there is not enough information to make that determination. There is a thing called micromets though (too small to see with today's technology) so even if nothing shows up on scans, they will likely want to do the chemo to kill off possible micromets.
Wishing all the best for the both of you!
Mike