From my personal experience working as a tour guide, the tour guides are often, but not always given a small gratuity from the tour free, but paid poorly so those tips really help. Drivers are rarely included. If I am going on an owner/operator tour, I do not tip as much to the guide when they are the owner, because you know they are paying themself well.
In my personal travels, I tip the bus driver if he/she is friendly, has the coach in a good location for drop offs and pick ups, has the temperature right inside (ie made sure the AC was on in advance of the pickup), and possibly helped to load cargo under the coach like shopping bags or strollers.
I give an additional gratuity to the guide if I enjoy the tour and feel like the guide does more than "the job". For me a tip is earned...especially on tours.
EDIT, I guess I did not completely answer your question...with regards to say a mushing camp. You will obviously have someone assigned to you to take you out, so that is who you would grat. At a lumberjack show, anyone that goes above and beyond could potentially get a gratuity from you...and you can base that on how/what they did.
For example, we went to a rodeo, and a worker there tipped us off to sit in a different area and sure enough, they were the best seats in the house. Afterwards, we found her and gave her $10 for the information because we had such a great time because of the info she gave us.