Cityfishing shared some wonderful information with me via an email message, and I thought that since the information is so valuable that I would post it here, although I don't know if it pertains to all chain hotels that participate with Bancotel, and that have point incentive programs.
Turns out that when Cityfishing stayed at the Westin Alfonso XIII in Seville, using Bancotel vouchers for payment, that because he is enrolled in the Starwood Frequent Stay Program, that the Westin Alfonso XIII credited him with points for the nights that he paid for with the Bancotel vouchers.
This is really very good news, its an additional incentive to buy the Bancotel vouchers when chain hotels credit your stays to their programs. You get a hotel room for approximately 50% of the rack rate, plus the points.
Although this might not work for all chain hotels that are in the Bancotel program, it is worth providing your membership number anyway. The minimum you should be entitled to is an upgraded room, if available at check-in, and a free newspaper in the morning. If all the benefits are extended, then you'll get points also.
This might also work for airline frequent flyer programs that credit frequent flyer miles for stays at certain hotels.