Ahhh....the old proto-Planetfall line. The tank pictured in the
OP was, near as I can tell, only ever a prieview.
I should point out though that even if it had been made, it would have been at a much smaller scale than
40k...closer to Epic. Would have looked good in a game of Titanicus probably!
The closest model to actually come out as part of the later Planetfall releases would probably be the tanks that came in the RSN assault helix: