We are trackless and went through a series of choices and came back to porta-potty arrangements. Cost and permitting were big factors. Spillage concerns were reduced significantly by only partly charging the units and cycling them through fairly quickly. We have various fork lift configurations, with most being 6K-lb or 10K-lb rated. Some of the LHD buckets can hang forks, but its not pretty trying to move these units that way.
Dry chemical units were costly and a spill could be more of an environmental as well as a safety issue - alkali etc. wafting around an underground mine, you know.
A vaccuum unit was put in service to minimize trips. It works well, but you then have to service the toilets with paper, and recharge with solution.
Can be a problem with the stench system until you get the crews and hoistmen on board with the system and schedules.
Oh, for the days of p--- ditches!
Hope these thoughts help.