As someone wtih LOTS of experience on care and feeding of NiCad, NiMH and LiPo batteries (lots of R/C car and electric R/C airplane experience) I can provide a few tips.
If these are NiCads then they may be salvageable but are probably toast. NiCads should NOT be left for periods of time with a near full charge. NiCads get “memory” and start losing capacity. They need to be carefully discharged for storage and then peaked prior to use. Some times you can use special pulse charges that fix the degradation to some degree, but it sounds like these may be beyond revival. If a track is ordering a whole bunch for replacement I suggest they work out a trade-in deal with AMB as the electronics are probably 100% re-useable.
Hopefully the new units use Nickle Metal Hydride cells which don’t develop memory and have a higher capacity per weight.
Anyone around here selling used for $100 or less?
If so I might be willing to risk cutting it apart with a dremel and replacing the batteries. For more than that it probably isn’t worth risking it.