Actually the beauty with SP and Cotton Belts being sold off, is that many other east coast railroads now have tunnel motors. For large scale this is excellent, because now the tunnel motors can be prototyped into many layouts across the USA and elsewhere. Here is a roster list I researched on the tunnel motors.
SD40T-2
B&LE Railroad
901,906,909,910 Note: (Is actually a reworked SD45T-2 now called a SD40T-3)
Southern Pacific (you knew this…right!)
8300-8306, 8350-8356, 8489-8498, 8307-8321, 8357-8371, 8499-8573, 8327-8341, 8377-8391, 8230-8299
Union Pacific
2849, 2853, 4799, 4890, 4963, 4972, 3805-3808, 8803
Saint Louise Western
9261-9301, Note: (Mixture includes SD45T-2 engines, could not verify individual numbers)
Burlington Northern
7049-7053
R.J. Conman
5353, 5361, 5372, 5409
N.Y.S.W. Susquehana
3012, 3016
Helm Leasing - HLCX
6106-6116, 6124-6145, 6149-6162, 6197
SD45T-2
Southern Pacific
9166-9208, 9209-9260, 9302-9313, 9344-9370
Cotton Belt
9157-9165, 9261-9282, 9283-9301, 9371-9380, 9381-9390, 9391-9404
Saint Louise Western
9261-9301, Note: (Mixture includes SD40T-2 engines, could not verify individual numbers)
Union Pacific
7875-7916, 8639-8869, 4369-4599
DMIR Railroad
410,411,413,414,417,419
Kansas City Southern
4501,4503,4505,4507,4509,4510
CN
401,402
Helm Leasing - HATX
925-945
Those are what I have found and I am sure they probably may have changed somewhat. But it seems fair to me that tunnel motors can be made because there is enough historic prototype railroads carrying them as of late.
Special Note: DRG had many of both models. Santa Fe is also said to have units, but I could not find the numbers that it used. If anyone knows the SF numbers or wishes to add to this list please feel free.