Conductive dust is evil. Even your phone will likley stop working if you get conductive dust into it. It's as bad as water, except gravity doesn't keep it pooled on the floor.

I searched a bit and found that "Trolley Assist" apparently refers to a system where large diesel-electric mining trucks use overhead lines for part of their journey. (You can do an image search for "trolley assist" and find examples.)

I guess this is the kind of thing I was looking for.