If anything belongs to Team 0 that means anybody/team can use it. If you but a Flip Flop in the Simgroup then the team that captures it will be allowed to use invetories or vpad in that simgroup the other team cannot.
If you want to have a different effect you will have to do some custom
scripting.
You say the team that owns the middle base, by this I assume you will be using a flipflop at middle base.
Make a seperate simgroup containg the inventories on team 1 to be powered
off when middle base is captured, do the same for team 2 inventories. You
will have to make modifications to function FlipFlop::playerTouch that
says if team 1 captured flipflop then powered down the simgroup for team 2 stuff and visa versa. You can place a generator below the terrain (out of sight) for each base and simply disable the gen when flipflop is touched. The
Dynamix final map Trident has a package in the .mis file for disabling a gen from the scripts. You could use this at the start of mission so no body can use an inventory intill middle base is capped. Or leave them powered at start and all can use inventories until flip flop is capped. It would not be too hard of a package to implement.