I just read through the Random Movement rules and I think a case can be made that the pivot is not part of the random movement which says that 'if it comes into contact, it is a charge'. You first pivot, THEN roll for how far the model moves randomly.
If so, the pivot cannot take you within 1" as it is not part of the random movement (a pivot is hardly random now is it ) and thus this tactic would indeed work on the HPA (or Steamtank )
And I kinda agree with Judochop, I don't really feel sorry for Skaven.
EDIT: I actually asked the same question here in regards to the Doomwheel: http://www.warseer.com/forums/showth...g-a-doomwheel)