no real policy.
However most guns with an APU in reality only use that to deploy to/from the tractor, and not to motor several miles down a road, let alone 1000m cross country. FH-70 does not have movement forex.
If you feel different - feel free to mobhack your own figures.
(Wish that 25 pounder I pushed through the Otterburn clag along with a dozen+ UOTC cadets had had one
!
Cheers
Andy