If you have vehicles available at the equivalent TL as the weapons it can be argued that military vehicles might have recharging outlets on board APC's for charging the dismount's weapons. The power plant on the APC could also be used.
That's basically what LBB:1 says when introduces the laser carbine and laser rifle. The question now is whether a given merc outfit is going to have those kinds of vehicles.
LBB:4 is oddly silent on the costs patron will incur to hire vehicles, or the hiring cost of any other equipment for that matter. All we're given is the monthly salaries of the mercs themselves and how many shares each will receive at that ticket's end.
GT:SM, a flawed book in many respects, didn't overlook equipment hiring costs. I remember running the numbers for similar sized units of light infantry, mechanized infantry, and armor. I'd expected substantial increases between each unit, but the rate at which hiring costs exploded as more "ironmongery" was added still shocked me. IIRC, you could get a regiment or more of infantry backed by tube/rocket artillery for less than the price of a grav tank squadron.
APCs and like will certainly be able to recharge laser power packs but, given the costs involved, how often will a merc outfit have APCs?