When Peter incapacitates Jason Lang, Lang falls with gun in hand and falls to his right, but the gun is seen behind him in subsequent scenes. Furthermore, Lang's hand is about 1 foot or so from the cell when Peter begins reaching with the mannequin arm, but much farther in other scenes.
The booking form for Jason Lang gives two dates of birth, one in 1986 and one in 1992.
It would have been obvious to two senior FBI Agents if Keller was planning to escape during his prison transfer some of those on the bus would have had to be complicit. Therefore they would have called in SWAT not contacted the driver direct.