I've read that only mechanical brakes work with road bike levers (I'm assuming that means the type that goes on the front of drop bars). Is this restriction the case with time trial brake levers that go on the end of bullhorn handles?
The Magura RT6 and RT8 Hydraulic TT brakes have been available (if somewhat unusual) since last year. They are a solid system which is compatible with most current TT frames. The RT6I've only seen as an OEM product. The RT8 seems to be the retail version.
Hydraulic STI levers from Shimano are expected on display at the Taipei Bike Show, going on this week, and an announcement from SRAM is expected in late May.
The photo below is a pre-release Shimano Hyddraulic STI lever seen last February on Rabobank pro rider Michiel vd Heijden's cyclocross bike.