He's against medicine, using robots in warfare and relying on technology, he's not against any and all technology.
Yeah, but alot of the stuff in Big Mt was being created for war, it was a Military Research Centre after all.
From the wiki "While the Legion uses technology when appropriate, there is no interest in the pursuit of technology in any aspect like there is with most other major factions in the wasteland."
So what would they be doing in a high-tech place like the Big Mt?
"Caesar firmly believes that reliance on technology weakens humans, and was responsible for the Great War."
If Caesar wants to revert mankind to the days of the Roman Empire of what use would the stuff there be to him?