If your drives/amplifiers are connected to a Heidenhain 150B then I will presume that the encoders will be sinusoidal and thus no use.
If however your control is a 150BR then it will have square wave output encoders, whether differential or single ended I cant say.
Regarding +/- 10v, then yes that will be the control signal they take.
I dont know what drives/amps you have so cant really say whether they have encoder outputs but I would guess that they dont as it is really only AC Servo drives that tend to have them.
Hood