Is that 4000 hp for traction or gross? Amtrak P42's for instance are rated at 4250 hp (so, more than 1000 hp/axle) but up to 1100 of that can be drawn off for head-end power (HEP) resulting in a net of 3150 available for traction. Of course, if more than one unit is used on a train only one of them is supplying HEP so the full rating applies to the others. Then of course there are the electrics - even the venerable AEM-7's have 7000 hp in a 4-axle unit.

Back to the original subject somewhat: does GE actually do Tier 4 without urea injection? Sounds like it. If they can, they may find markets beyond railroads - DEF is required for all stationary backup generators I know of in CA at least (probably nationwide per EPA standards), and that can be a pain to deal with in cold climates or where the thing operates (and is maintained) infrequently. If GE can produce smaller versions of a no-DEF engine for gensets, they might just carve another piece out of Cummins' and Cat's business.