I visited the center TT area on Trinity twice last night, and even drove around for a bit; nobody there. Evidently, I should have checked back later in the evening.
Given it's specialized nature, and intermittent availability, I still think TT would benefit from some sort of tweak to encourage use. For example, if there was something interesting to do there for the first player in, that player might stay longer until someone else joins. Once you have 2 people fighting, then the momentum would presumably build.
I hate to say it, but perhaps a capturable vehicle base right in the center? The first guy in could begin the process of capturing it, and subsequently it could function as a focal point for some of the combat.