My wild guess:

BNSF doesn't have that many modern EMD large road units compared to similar GE models. So the odds are in favor of GE to begin with. Someone familiar with BNSF operations might know if they have assigned or prefer to use the EMDs on a certain territory or type of train. It may also have to do if there are certain shops the newer EMDs are assigned for maintenance or warranty work.

In NE Oregon we see a steady parade of Union Pacific GE ACs with quite a few SD70 types (DC and AC) mixed in. An occasional heritage, CP, CSXT or NS unit breaks up the monotony. SD60 types, GP60s and a few GP39/40-2s handle the locals. Every now and then you might catch a Dash 8, SD40-2 or other four axle but that is rare.

I can remember spending many days on Cajon now many years ago where Union Pacific ran mostly SD40-2s almost to the point of being boring, though a few DD35, Centennials or GEs might show up. Southern Pacific relied on a pool of U33Cs, SD39s and SD9s but just about any road unit could get thrown in. Santa Fe probably had the widest variety at the time with plenty of U boats and EMDs mixed together, and it wasn't uncommon to catch trains using pure sets of GP30/GP35s. At night it was easy to tell what train was approaching - SP used gyralights, UP had the Western-Cullen rotating beacons, Santa Fe had the solid state yellow beacons, and Amtrak had strobes. You could also hear if the approaching consist was EMD, GE or mixed.