Yes.
A typical mach tool change for me would of been-
Code:
G0 G53 X0 Z0
T0101
I say would of been, because I no longer use Mach, but I wrote enough code to know how to get it do what I wanted it to.

G53 should be valid, as it's telling Mach to use Machine Coordinates (i.e. ignore any tool/work offsets). The only thing I can think of, is do you have a good homing routine, with the axis referenced LEDs turning green after homing/referencing?
Something tells me if the machine isn't referenced, then machine coordinates might not work.