I am afraid this is not correct as there are always 3 signals and they are equally spread along the 360 degrees of one revolution, meaning there would always be a 120 degrees phase shift between them.
Yes thinking about it thats correct, will have to look into it when I get a chance.
The commutation signals are only used at startup as far as I am aware so once the motor is moving they are not used, some of the S type motors (similar to H) had hall signals rather than encoders with commutation tracks, again will have to read up on that.
I remember reading an article a few years back which showed the difference between BLDC and AC drives and it had some nice animated graphics showing how the poles were energised in either case, will have to see if I can find it again.
Going back to your motor,
IF the Ultra 5000's support Self Sensing as the Ultra 3000's do, then even one of the cheap encoders from US Digital should work for you. You probably would need to make a line driver as well, but no big deal in doing that
Hood