Each case is its own animal. BNSF is conducting a (questionable IMO) strategy on their Northern Transcon to give oil priority over ag products - Bad Will hangs around for a Long time. BNSF has bought many locos recently but the track capacity has not kept place.
OTOH I’ve noticed that UP insiders complain about investments in shiny new DT but way too many inadequately maintained engines that can’t pull to keep up the flow of traffic. Go figure.
Don’t think we’ll see much push for triple tracking - two mains and maybe a few staging sidings will go a very long way vs single track. The 3MT ‘gap’ in the BNSF San Bernardino sub north of Highgrove is very short in the big picture. Likewise they are letting the publicly funded grade seps in LA and Orange County set the pace, obviously no big rush.
UP isn’t pushing much harder on the Sunset Route - 30 to 50 (?) new miles of second main a year. If they were really hurting you would see a contractor led ROW grading blitz in CA and AZ. Show me the contracts!
Just a suggestion, but discussion of further BNSF expansion could be moved to these topics: