I saw some DL and AA 175's going around today. Not sure who was operating them though.

No. Its also DL and soon to be AS..

Correct, but only for the 175. There are no AS or DL CRJ's in SFO.

Once in a blue moon you'll see a DL -900 trip originating in SFO. But they go super senior and they're so rare that they're pointless to even consider.

So DEN won't be all UAX soon?
Or is this SFO?

I'm not so sure AS 175s will be based there.

DL 175 are not based there yet there are DL pairings... define "based"...??.. there will be flights there and SJC. More troubling is will they want a SFO/SJC co base??? Im hearing BOI is on the table.??? Form Denver training facility.

I wouldn't be surprised to see some the AK 175's shifted to LA/SF as QX spins up their program.

Not sure anything about QX is looking up these days.

Where did the BOI rumor come from and what's the legitimacy of it?

A ton of airplanes overnight there, giant MX hangar, and service from multiple partners.