I believe those are the actuators to "raise or lowerl" the center set of wheels (if it's the new design GE is testing, they have no traction motors). This effectively makes the trucks a convertible B/C configuration saving output of energy (and thus fuel). I think once up to speed the center axles are lowered and while “coasting” only serve to distribute weight.
They almost look like brake cylinders until you see the lever over the middle axle. If so I think it's a goofy idea in the first place. I mean, why not just let middles coast anyway ? What is really being gained by raising and lowering the mid wheels/axle if they'r coasting blind to begin with ? What, saving 8 brake shoes ?