So does anyone happen to know how much of a maintenance reduction there will be on 2926 vs. other mainline excursion steam locomotives because of the roller bearing rods?
Just like N&W 611 and C&O 614, both with roller bearing rods, soft grease is done only once a day, regardless of milage that day.
Obviously there will have to be inspection of bearing lube levels but will maintenance at stops be less than on a similar locomotive like 844/4449/3751/261?
You can NOT inspect "lube levels" on roller bearing rods as they are sealed. Simply apply small amounts of soft grease each day. Locomotives with plain bearing rods, generally receive hard grease (Pin Dope) about ever 100 to 150 miles (at least that is what happens on 4449), which is done with a large compressed air operated Alimite Gun.
ATSF used to run the 2900s from La Junat to LA without a locomotive change (~1200 miles) so I assume the roller bearing rods play a roll in this.
Yes. Just like NYC roller bearing equipped Hudsons and Niagaras, only fuel, water, and refilling of the mechanical lubricators is done at about 250 to 500 miles, depending on the terrain.