You don't mention if these all share the same common? I would assume they do?
You can obtain 24v that way but it all depends on how and what it feeds and if it is a completely isolated circuit, if it is then you should see no problem.
The problem may appear if you operate any of the other supplies into the driver.
Or if you are using either of the +12 -12's to operate any other piece of the equipment.
IOW, the whole picture has to be known before giving a decision.