I believe the question you are asking is about power sharing among the class 1's? I think all the class 1's have a pool of power in which they draw from and some may owe and others have excess.
As far as ATSF using CSX power, sure. In fact heres a pic of 2 sd70m demos, csx purchases, working in Cali:
EMD SD70M Demos - SoCalRailFan Photo Gallery
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Athearn PA1 #75, SD70M #2588, custom C40-9W #8907, and Tower55 ES44AC fantasy paint SP #399
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