It has become somewhat of a common practice to keep the same units on long-distance run-through trains. So, these "foreign" locomotive units, such as BNSF, UP, etc. proceed on CSX rails as the lead unit of the train, usually all of the way to its destination.
Of course, the engineer / conductor reports the train and locomotive # when approaching key signals, interlockings, junctions, etc.
In an effort not to be confusing about locomotive numbers, the radio report "Train U26-26; engine UP 5214, northbound, Folkston Turnouts" is given. This is done to avoid confusion, since CSX also has a 5214 locomotive unit.
Sometimes, a CSX terminal may be short-handed on CSX locomotive units, and if a "foreign" locomotive unit is available, it will be assigned to a CSX short or medium distance run.
These locomotives are not leased, they are "borrowed" on a short term basis, with a record of the horsepower usage by the hour being recorded while on CSX, with CSX locomotive units being used on UP, with similar time-use records being kept.
Nothing "fishy" about it. Just good common sense judgement. It's not indicative of some "take-over" plan or operation at all. If that were so, then at least 10 different railroads are going to take over CSX or vice versa! Because I've seen lots of FerroMex, KCS, CP, CN, BNSF, UP, IC, QNSL and other railroads' units roaming on CSX as far southeast as Florida!
CSX also leases locomotive units from commercial leasors such as Helm Financial (HLCX, HATX, etc.), CIT Group (CEFX), and other companies.
ACLfan