At the Banercito doing paperwork we noticed a sign that indicated Hoy no Circula is sort of suspended for those driving vehicles not from Mexico - in other words US or Canada. It looked like it mainly...
The problem I have encountered is the predator/prey syndrome with transitos (not PFP Caminos Y Puentes). They develop their own interpretation of the Hoy No Circula area of operational validity. So I gave up and argue no more. I bypass the entire mess by traveling east around the state. Sn Juan del Rio - Tlaxcala - Puebla. Public transportation when I actually go into the city. Others may have had better fortune - I envy them.