When you call, be sure to be very specific about what you want done and what they will be doing.
The other Bobtail 1911s on the market combine a full sized frame and a Officer's Model size MSH...which is the shortest in current production. The EMP already uses this size MSH. The Bobtailed EMPs that I am familiar with have been custom cut and welded jobs and cost a lot more than $170 to fabricate. They can be done, it is just a matter of cost...not too surprisingly most top tier 1911 smiths aren't also Master Welders.
I might be wrong, but I think what The Springfield Armory Custom Shop is offering, if they offered anything in that vein on the EMP, would be something like the Round Butt option offered by Dan Wesson
Their price for the modification on the full sized frame is listed as:
1. Modify frame for “Bobtail style” mainspring housing (Mainspring housing included) $225.00*
*Requires refinishing at additional charge. See Refinishing list for additional cost.
2. Armory Kote™ frame & frame small parts only (Specify Flat Black, Matte Black, or OD Green) . $ 80.00