For a while there were two different 15/12 programs in effect.
One was for new Florida Resident passes which expired December 31, 2009.
The other, which is still in effect is for renewals of APs and is valid until August 31, 2010. Although the notice does say the program can be changed at any time.
If you are talking to someone at Member Services, tell them to go into The Hub and look under Work >> Ticketing >> Guest Offers >> Passholder Promotion: 15 Months for the Price of 12 Months. Unless there is something they have, in writing, which contradicts this the program is still going on.