Pacers are allowed and encouraged at all times. Pacers' times and/or distances can also be listed in their own section of the race results. Pacers can ride a mountain bike, run, or do a mix of both.
A no-muling rule would be difficult to enforce and could, in certain circumstances, make a bad situation worse. So, pacers and crew are allowed to carry things for runners to eat, drink, or use. Everyone out on the course should help each other achieve their goals.
If you want your crew to know where they're going, please give them a good set of maps using the link on the course page. For mid-course parking, the several road crossings are great places to park a vehicle and meet your runner. Except in an emergency, no crew vehicles are allowed to drive on the rail-trail portions of the course.