There is no restriction from EU OPS about the number of autopilots. In fact the A320 has a dual autopilot system as well, not triple, and of course were are working under EU-OPS rules as well.
Boeing offers a choice between two different manufactures for the 737 autoflight system, Honeywell and Rockwell Collins. The Rockwell Collins autoflight system is allways fail operational capable, however you need to order some additional stuff like the autopilot rudder actuator and the ISFD which serves as the third attitude source to be able to use the fail operational stuff. Most airlines want to save a few bucks, especially for the maintenance of the rudder actuator and dont buy that which limits them to fail passive operation.