Almost all amateur triathlons are DRAFT ILLEGAL. This was originally because triathlon famously has its roots in finding out "who the best athlete is" (Ironman, specifically, was founded by a group of friends who each specialized the different sports, and each thought that their sport was the "hardest"). In that context, drafting was/is seen as taking advantage of another athlete's work and thus counter to the point of the competition. Today, most triathlons remain draft illegal for several other reasons, including:
- reducing the danger for athletes who may not have experience or feel comfortable riding in a tightly packed peloton
- balancing out the potential gains of the three sports; allowing drafting on the bike results in a much larger focus on the run at the expense of the bike and especially swim legs, where spending extra energy to attack the group is frequently (though not always) a poor tactical decision.
- reducing congestion in the transition area; having riders arrive at T2 in packs of 10 or 20 or more would be incredibly chaotic and, again, dangerous at most venues.
You say that the course is too narrow to pass, but 6 feet wide seems like plenty to me. It is possible you may not be able to pass immediately (such as if another competitor is passing), but it should clear relatively quickly (this is another reason draft-legal would not work; that ISN'T enough space to have an entire pack ride together safely). Just make sure to call to the rider in front of you before you pass so they are not surprised when you go by. The rule triathlon uses, IIRC, is that you must maintain 3 bike lengths separation unless passing, and once you initiate a pass, you have 10(?) seconds to complete the pass or yield the 3 bike lengths.
If you are unsure about any of this, you should ask the race director. They will be able to tell you for certain what rules the race is being run under, although I'd be 95% sure the race you describe would be as I've described.