can any aircraft geeks here provide interesting information on this situation that happened last night?

The captain comes on PA shortly after door closes last night, A319 SFO-EWR, and says that we need to wait a few minutes for an engine start unit to arrive, and apologizes for the lack of aircon. My question -- does this mean the APU is inop? And are they relying on the other engine to restart in case anything goes wrong in the air? And what exactly is the ground cart supplying to start the engine? Air? Hydraulic? I saw the cart outside my window, like a large generator truck -- it must be pretty powerful!

thanks!