I cannot "trackstand" per say, but I can pause for 3-4 seconds before starting again. I have to say that trackstanding is NOT the fastest way to start from a stop. I put my pedals at the 1 o'clock - 7 o'clock position with my right foot strapped in the 1 o'clock positioned pedal. When light turns, I "throw" my bike foward pushing off with my left foot on the ground. The resulting mash from the right foot accelerates me quickly and I sit in the saddle. The following rotation I flip and strap my left foot to continue accelerating fully strapped. I could do it standing if I wanted but usually accelerate fast enough just seated.

I think my problem with trackstanding is I am trying to learn to do it with my backpack off. When I'm commuting, I'm tired and weigh 20+lbs more up top.