The HSP-46 is the US's newest diesel passenger locomotive, created by MotivePower, Inc. in Boise (MPI) and General Electric Locomotive for the Massachusetts Bay Transportation Authority (MBTA) out of Boston. The engine features a 12-cylinder GEVO engine producing 4650hp (same as the ES44 series), which is then fed to 4 AC traction motors and a HEP inverter. (My guess is that HEP will burn about 500hp, leaving ~4000hp at the rail.) MBTA ordered 20 of these units back in 2010, and has since exercised options and upped the order to 40 units.

MTBX 2003 came south out of Denver on Friday afternoon, and I found it sitting around the Pueblo yard on Sunday, 27 Oct 2013. It's headed out to TTCI for testing and validation. Note that this isn't the first of the HSP46s to make it out the door - MBTX 2001 has already been painted and shipped to Boston. However, from what I gather from the interwebs, but apparently is only being used for PR, training, and familiarization until the 2003 completes testing.

I'd expect BNSF to move this to North Avondale either Monday or Tuesday.