Do you get a lot of UP running in your area? I believe UP and BNSF share trackage rights with each other.
Around here they don't share any trackage rights, but for rail-fanning, there are many main lines that are within easy driving distance. UP has a main line from Ft Worth that runs through the nearby city of Denton TX, the line that UP 4014 used yesterday. It is an ex-MKT/TP joint line. It is quite busy with grain, coal, autoracks and mixed freight. Average daily train volume is 32-35 trains. Their line from Ft Worth to Dallas has over 100 trains daily.
Even busier and closer to me is the BNSF main that runs from Ft Worth to Oklahoma City and north; a former ATSF line. From near Denton to Ft Worth, it parallels the UP line about 4-5 miles west. It holds some extra significance since there is an interchange with KCS about 12 miles away. While it is primarily an intermodal well car traffic lane, probably 60%, it is also used for grain for export, petrochemicals and plastic pellets from the Houston area, autoracks, oil and some mixed freight. There are 80-85 trains a day, including a trip each way by Amtrak's Heartland Flyer. There is an afternoon interchange of trains with KCS every day at a place called Metro Junction, (Dalton Junction in ATSF days), and in the evening, a KCS train runs through to the Alliance Yard, to interchange intermodal cars, both TOFC, COFC and well cars. There are 6-10 trains daily on the KCS line.
A former rail-fanning location for me was the BNSF main (formerly Frisco) line from Sherman TX to Dallas. It ran alongside the place that I worked for many years. No unit trains there except a daily rock train from a quarry NE of Dallas. It had all mixed freight which made for the most interesting traffic of all. While I worked there, there were 20-25 trains daily, but I have been told that the number has since been reduced.
Also nearby where I worked was a yard for DG&NO that interchanged with BNSF and FW&W out of Ft Worth. It as a hard place to watch because it had a residential neighborhood on the north and an industrial park to the south.
Lots of rail-fanning locations for me. I hope that I haven't bored anyone.