I had an online chat with Avis customer service via avis.com

Was told that all rentals since Jan 1st 2015 will be counted towards the 12 needed for preferred plus status. However, only rentals that are initiated on July 1st or later will accumulate points.

Unfortunately the rental I began on Monday June 29th and returned July 2nd will not be counted for points. This further delays the 250 point enrollment bonus, which posts 72 hours after a post July 1st rental is returned.