That's a real BIG assumption Riley considering the tank was dead in its tracks for a reason.......what happned to the occupants who obviously had personal knowledge about its functionability?
You jump into that death can and you're stuck until you either come up for air, die of thirst or die of starvation since there's a whole lot of zombies hanging around that "fast food tank" waiting for their take out meal..........
There was one (infected) inside the fighting compartment and the rest were outside, nowhere in evidence, when they disappeared. Or dragged out of the hatches while unbuttoned. Looked like they got caught away from the tank. Otherwise there's have been four live crewmen, or four bodies, or no one at all inside the tank.
Then again this is Walking Dead, not real life. There were M2s with belts in them in the positions in front of the CDC.