Probably not. Iirc from reading up on these many years ago they have a read-protect circuit which is literally burned out by the manufacture after the cpld is programmed. It can't be un-protected - this scenario is exactly what the protection is there to prevent. 
DCE/Phase5 would have wanted to protect the IP contained in those chips, so it's almost certain they will have protected them.
The read protect feature on MACH chips works basically the same as a GAL chip. The same is true for most other CPLDs but they often have different/proprietary methods for programming it.
Nothing is "Burned Out" in these EE chips but you have to erase the whole CPLD in order to reset the read protect function.
