My son and friends have done similar rides here in Oregon. There have also been multi-stage races in Eastern Oregon. They do bring in tourist $$ into the area. I don't believe they have ever presented a parking problem cause Sumpter and McEwen are not a major stops for cyclists (my son sez don't use the word 'bikers', cause that word is used for those that have combustion going on between their legs, cyclists use their legs for propulsion).
I was not on duty, but I understand a couple years ago a bunch of racers got delayed as Train 3 or 4 passed over Hwy 7 with the gates down. I wonder how their race committee compensated the group for that, cause the lead bunch passed over before the train got there, and the delay must have really widened the gap.