Bret, much of the information you are interested in can be gleaned from the ICC structural valuation survey of October 1916. Ron Brinton’s post of 21 Dec 2000 says it is available from the SVRR gift shop <
depot@oregontrail.net> for $25. The report includes dimensioned floor plans, descriptions of construction materials, and inventories of equipment at some locations.
At one time or another, there were depots at Baker, Salisbury, Lockhart, Thompsons, McEwen, Sumpter, Whitney, Tipton, White Pine, Austin, Dixie, and Prairie. Some of these were just unheated enclosures. The depot at Austin was a substantial structure, befitting Austin’s status as the hub of operations at the west end of the line. The Austin depot was similar to the depot at Tipton. SVRy did not have a depot at Bates, but the railroad used the Oregon Lumber Company Hotel as a depot at times.