This is an old thread that got resurrected somehow (as old threads tend to do). The problem is that the linkage for the door latch is shared with the lock/unlock. You can replace the whole thing with electrical solenoids and just use switches to both open/close and lock/unlock, but that's a pretty radical mod when all you want is power locks.

Since I started this thread, another gentleman from Belgium posted a solution that he came up with that would allow you to use a linear actuator to lock/unlock while still allowing you to use your mechanical door handles to open and close the door. He added a second lineage to operate the latch and used the original linkage to lock/unlock the latch.

By coincidence, I had my door latches out of one of my doors at the time he posted this, and after studying his photos and looking at my latch and linkage in my hand, I concluded that what he had come up with would work.

Good luck,
-DV