Prometric posted an update on their partnership with us--touching on many of the points you have asked about; you should check it out. Your comments are welcome here, but send a copy of whatever you say to email@example.com while you're at it. Here are a few bits I know many of you are interested in...
"Each test center worldwide manages and sets their individual business hours to meet their customers' needs. Many testing centers provide weekend and off hour testing."
"Prometric's schedule, reschedule, and cancellation policies are as follows:
"All test centers, including IT Academies, can become a Prometric testing center. There are no additional costs or exam delivery minimums to meet*, however, centers are required to meet minimum hardware and software requirements.... *Although there are no exam delivery minimums to meet, there are exam delivery minimums to meet in order to be compensated for exam delivery."
"...we have staffed our Global help desk with over 125 employees providing support in 12 languages through phone, e-mail, and eChat."