I was told by the FAA guy in Los Angeles many years ago (and I have not asked since then, so they may have changed their mind) that the entire reason for the LMR category was that it was not to be waived and they wanted to have people do the notification. In other words, even if there was a waiver for what we consider HPR (the FAA does not use that term), you were still expected to notify for LMR.
There is nothing legally preventing you from applying for a waiver for any or all of the FAR, including the LMR notification requirements, but why do so?
I know why I asked originally (it all comes back to me now...). We had a problem with the airport manager who went ultra-negative over our faxing in the notification for LMR. We contacted the regional FAA guy who handles waivers and all issues from Model Rockets upward. He had no problem with our launch site and even spoke to the airport manager but got nowhere. We asked the FAA guy if we could just waive that notification section and he said "No", and explained that a lot of thought went into the addition of the LMR category and the requirements and that we needed to follow the procedure. Eventually we worked things out with the help of many levels of management at the County Parks Dept (the airport manager is a contracted employee of the County Public Works Dept which owns the airport).
I hope this info helps.
-Fred Shecter