But I can provide the exact quote of what John Eaves said about what happened with Geoffrey Mandel.
That's called hearsay... and it's possibly a tongue-in-cheek interpretation of the situation.
Besides, if he was using company time and resources for a side project, especially on a production that was so concerned about secrecy, then it wouldn't be so unbelievable that he'd be fired for that. Perhaps he wasn't authorized to access the Enterprise design files, or perhaps the producers were concerned this project was something that could be leaked or something that he intended to sell.