Dan
If you are a contractor in any capacity, I would recommend calling your local epa office, as they are the entity that administers the god-forsaken and ill-fated rrp program. The impact on the sander is not a big deal, as the extraction is so thorough. You might just blow it off with a compressor and wipe it down with a damp rag after usage. Proper care of the filter and bag in the extractor is the fundamental issue. My company is rrp firm certified in my state, and my understanding upon completion of the excellent training course was that there may be some variation from state to state, as well as overlap and ambiguity between the rrp program and other state administered ones such as osha. That is why you should check with your local office. I am fairly certain they will tell you to dispose of the filter and bag properly, meaning to put it in a heavy duty plastic bag for disposal, but the mil thickness of the disposal bags is a detail that, according to the program, must be handled correctly. I believe that in some situations, double bagging is protocol.
If you are not a contractor, and just a regular homeowner, none of this applies. I assume your neighbor is not a contractor. If there are small children in the neighborhood, I applaud your willingness to lend the gear. It will not harm or contaminate the gear a bit. And could prevent some unsuspecting child in the neighborhood from exposure. That is what sucks is frustrating about rrp. Contractors have very strict rules that they must adhere to in the performance of lead work (at the risk of $37k/day fines per violation), and meanwhile, homeowners are free to grind lead up and blow it all over the neighborhood.
So, call, explain the situation, and cover the bases. It is not without the realm of possibility that some neighborhood watchdog could report what might be lead getting sanded in the neighborhood, and it would be best if you had called first.