From what I can tell, Gibson were using the 9V XTCT pre-amps in Tobias basses, around the mid-nineties, before they moved to an 18V setup with the NTMB-918 pre-amps. I used to own a '95 Gibson Tobias Classic 5 that had an XTCT and the same Bartolini RT pickups with the curved shells and logo. (In fact, I still have that pre-amp and pickups in my spare parts box, as I upgraded the whole setup with Bartolini BC pickups and an Aguilar OBP-3.)
Before that bass, I owned a '98 Killer B-5 and that had the 18V NTMB setup, but similar pickups. I've just recently received a 2006 Killer B-5 and it has the later, single module NTMB-F pre-amp and a single gain-pot on the top.
Cheers,
EG