The parking brake functions like a drum brake inside the rear rotors.
If it was just the rear pads that were replaced, it shouldn't have affected the parking brake.
If they replaced the rear rotors, the LR4 needs to be put into a "service mode" before they are removed. Then, there's a bedding procedure to bed the parking brake pads into the new rear rotors. I'm not really sure how not doing all this would lead to them locking up, though.
I had an indy mechanic replace the rear pads & rotors on our old LR3. About 3 days later one of the rear brakes locked up. That awful burning clutch smell, blue burnt rotor and super hot rear wheel. Surprised it didn't melt the tire bead. Sure enough, indy had no clue how to put the parking brake in service mode.