ABS system locked up after new braking system put on

I recently had new brake pads, rotars, lines, calipers, and master cylinder put on my car. I drove it home and it would go over 45 miles an hour. Drove it again and it did the same thing. Took it back to the mechanic and he said the ABS system is locked up due to someone putting in the wrong kind of fluid.
My question is, is that possible after all the new brake system was put on and fluid was out, since lines were replaced, could putting wrong fluid in a long time ago just now cause the ABS system to lock up and the car act like brake pedal is pushed down at all times even when you are trying to drive?
Thank you
DAB