Only B units in the US are the GP60Bs running in the Pacific Northwest on a dedicated service (fairly certain it's a branch line) always running with GP60/GP60M leaders. BNSF even went to the trouble of recabbing several as a test program.
If they had cabs I'd wager the XRBs would never have been stored at any point in their lives....
The XRs had a problem, because the frame wasn't long enough to allow both a full size EMD radiator and a crew toilet. The XR radiator it the same as the A (and possibly N) class locomotives which are only 2250 HP into the generator compared to 3000 HP into the generator.
This hasn't stopped VL class working ore and concentrate trains in the Northern Territory.
But the XRB has the full size 3000 HP radiator, like a C or G class.
Since there was no room for a crew toilet, there was no cab.
You can't just fit a cab because the XRB had different dynamic brakes of higher capacity than the XR which occupy the space of the cab anyway.
If you fitted XR dynamic brakes and a cab, there would still be no toilet.
You could fit the smaller radiator, a toilet, a new cab and new dynamic brakes...
But even if you took the cab, dynamics and toilet from an X class, with new radiators, it would cost quite a bit.
PN probably don't want a 3000 HP unit that badly...
Maybe they could sell them to SSR who run a lot of trains with multiple locomotives.
I'm sure they could use locomotives without cabs.