I think these are just the Tier 3 models with just 2 traction motors in a 3-axle truck. It is called ES44C4 since it has just 4 AC traction motors & is supposed to replace the ES44DC locomotive that GE used to offer. These locomotives are mainly bought by BNSF for their non-coal, non-taconite trains. Here in Central IL, I have seen these mostly leading intermodal trains. They have been displayed at the annual Galesburg (IL) Railroad days for the last 2 – 3 years & I got this information from the GE employee (one of around 50, who work on site at the BNSF Galesburg yard) who answered the questions of visitors who went inside the cab of this locomotive.
The linkages on the center axle (without the traction motor), lift or lower the axle as needed. They have the same layout as a regular ES44AC for ease in maintenance to folks who are used to maintaining GE’s usual 6-axle locomotives. Florida East Coast Railroad also started buying these ES44C4 recently.
From another forum I visit, I learnt that GE apparently had enough emissions credits to continue building Tier 3 locomotives past the Jan 1, 2015 Tier IV deadline provided they build a Tier 4 locomotive for each Tier 3 locomotive built. They plan to keep building Tier 3 locomotive until the middle of this year, Tier 4 starting in the second half of this year.
These are just my opinion,
Thanks,
Naveen Rajan