A few examples of similar stuff in Northumberland too. Though often the undersides of undeniably BA cists look very fresh, due to the lack of exposure, so some CnRs were obviously still being made in the BA. Then there are those quarry sites like Fowberry North Plantation and Hunterheugh where the quarried motif has been replaced by a newer probably BA motif.

But then there are sites like the Fowberry cairn, which looks a lot older, as if it'd been weathered for a goodly while before being incorporated into a cairn. As it was facing inwards in the cairn, you've got to assume that the weathering took place before inclusion into the BA monument.

As regards the pushing back of dates, I think that lower paleo site in (Chattan?) India, is supposed to be simple cups, mebbe the more complex stuff is a later elaboration on the theme. I wouldn't know one way or the other about the Irish stuff, but I'd be fairly sure that if there was open air RA in the area, the builders of the monuments would be tempted to re-use if they could shift it easily. Given that people were prepared in some places to actually quarry outcrop, it seems a lesser act to move an earthfast boulder (i.e. less chance of dodgy ju-ju from the ancestors). But that's just speculating on the midsets of the ancients, not hard evidence of anything :)