Have you checked out this site:

http://www.alleycat.org/

We work with ferals daily. We TNR but only where there is someone that will be providing food and water for the cats. You can relocate them, but there is a process to follow to do this. There are many no-kill shelters, do you have any in your area? http://www.saveourstrays.com/no-kill.htm

I don't think it would be a wise decision to release the cat to the area where the building will be demolished.

Ferals can become tame and a pet. We have 17 at home that were feral at one time. It just takes patience.

Contact Alley Cat Allies and tell them your situation, they may have suggestions or places to recommend to contact. Good Luck! Let us know what happens.