"Check first if your number can be ported into Google Voice:
https://www.google.com/voice/b/0/porting?pli=1"
Yes, I have already done that test. The number is eligible for porting to GV.
"If you are able to port, then you should be able to use your current T-Mobile number that you ported from your landline as a forwarding number."
I understand that. But subsequently I am going to
port that T-Mobile number to this GV account. Are you saying GV won't object to having
already used this number as a forwarding number while setting up the GV account?
Thanks!
Steve's updated advice completes the process. The answer to your last question is yes.
You may want to use your T-Mobile number that you ported and have confirmed as portable to GV and not your wife's. The reason is just in case you want to use your wife's cell number (or she wants to open a GV account) on another GV account (say for her) and need to use her cell number as a forwarding number.