No Pemex stations have the UBA sign yet for their diesel, and I wouldn't expect the attendants to know ANYTHING about the fuel, so looking at signs or asking at the stations is typically not productive. It is Pemex policy not to place ULSD signage (UBA) on any station until EVERY station has UBA.
I have personally drawn fuel samples at several stations in the Northern Baja and had them tested in the USA. They were all ULSD from the USA or Japan, which is consistent with the Pemex official information, even though no stations have UBA signs.
At this point in time I am confident that the stations list and information about main transportation routes is reliable.