Earl is exactly right, neither #15 nor #19 are MU.
The two "big" units at GTL are (I think MU). If the C&TS is in the market for diesels (and they ought to be) the bigger units should be the subject of some sort of lease.
I will be hanged for this, but I have always thought C&TS should have been looking for diesels to back up the steam operation. The "ones that got away" were the C-C GE "70-tonners" (MU) from southern NM (sorry, lost the name of the operators) that were sold for scrap to Birmingham in the 1970's. I bought parts fron BR&L for the GE 70-tonner on the Graham County (NC)as these ng diesels were, from the running board up, a pretty standard GE 70T. A grand opportunity lost at the time.