Yes, but remember Platinum/P1/CL can assign these seats prior to this. your chances are.... slim at best.
No I would not think it likely.. If it's assigned to you then they would sit in regular J and even if they asked should be told nothing's available. This is definitely a first come, first served situation imo*
(* of course, we have all heard stories of seat swaps being done for CL and seemingly entitled VIP's, but I've not seen this myself, and as a P1 never asked for or expected any kind of thing like this). So never say never, but I would not be worrying that some higher tier member would come along and usurp me in this situation.