Shilo Inn and Mammoth McDonalds are maybe 50/75 feet apart, share an open parking lot and ESTA and YARTS busses park in same location. My guess is the arriving ESTA bus and departing YARTS bus "connect." If ESTA is running a few minutes late, my sense is the ESTA driver would call the Shilo front desk, who in turn would tell the YARTS driver there is a slight delay, or possibly call the YARTS driver directly. If bringing a cell phone, program the Shilo Inn phone number, YARTS, ESTA, etc. It is a small community and my guess is they are more than willing to cooperate. If you miss the YARTS bus, just make a handheld sign with Yosemite printed on it and hitchkike. You should be able to find a ride to Yosemite; once in the park, can use the Yosemite shuttle bus.