The way it looks, the temporary pillars are there to replace the concrete pillars for a time while they're removed in preparation for demolition of the bridge or replaced with new ones.
Here's how I think it could be done: they'd dismantle parts of the bridge like the walls to reduce weight, then cut the deck in pieces corresponding to the division of the pillars, then remove the concrete pillars. The bridge would be supported by the temp pillars at this point. Finally, they'd lower each section of the deck on to a flatbed truck by ratcheting down the temp pillars, aided by a crane to keep it steady and orient each piece onto the flatbed.
Once the walls are removed, the deck is cut, and the concrete pillars are removed, lowering the deck in a few pieces would not take long. They could do it overnight.