Hi fredgrav and thanx a lot for your reply.
But have a look again to FCOM 1.21.20 P5 in the section "pressurization"..There is the description of the Take off phase:
"To avoid a pressure surge at rotation, the controller (either SYS1 SYS2) prepressurizes the aircraft at a rate of 400feet/minute, until the delta P reaches 0.1PSI. At lift off, the controller initiates the climb phase."
So there is actually a pressurization during take off roll. So the question, unfortunately, remains open..
