I just noticed you are a new member of H-M. Welcome aboard!
Not all that common. But there are a few machines set up this way. In the mid 80's there were a number of machines built that had factory CNC/Manual capability. Most were 2 axis, some were 3 axis. As far Is I know, all had Anilam controls on them. I just happen to have one of them.
There are many options to upgrade machine controls from really cheap to crazy expensive. It really depends on what your end goals are and of course your budget.
The servo motors and drives on that machine are probably brushed DC servos, and they are pretty much bullet proof, so in my opinion that is a really good starting point. I am a real fan of those motors/drives. That would also mean you that you have the most expensive hardware all ready installed.
I have done several machine upgrades so I'll be happy to help guide you through the swamp of trying to figure out what you need to do.