I believe it is prudent to use pressure-treated plywood when mounting a residential electrical panel against a concrete basement wall. I am in the Northwest USA where concrete basement walls often have quite a bit of moisture.
But I never understood what kind of fastener to use. Usually the plywood is only 3/4" thick, meaning I can't use most any exterior-rated screw due to being too long. I could use small stainless screws, but then I have stainless in contact with a bunch of plain steel. Probably not a huge deal, but it would still be nice to avoid it.
On top of all of that, and most importantly, I have nowhere to staple my cables. Every staple or cable fastener I've seen uses a plain or zinc-coated fastener (eg, NM-B staples), which I assume would corrode readily when in contact with pressure-treated plywood.
What exactly are you supposed to do when seemingly all electrical equipment is not meant to be in contact with pressure-treated wood, yet it is often required to use it?