The 377s in use with Southern use the same Dellner coupling system as the Network Rail Class 57s anyway as do South West Train's Desiros; my only comment is that if say a class 450 fails at Woking and a Class 444 sent to rescue it fails as well upon coupling, would Network Rail be dispatching a Class 57 to haul the trains out of the way so a service can be resumed asap?
I don't see why Network Rail would be responsable to recover a failed train unless it was one of their own, I thought that part of the franchise agreement the TOC/FOC was responsable since they run the service and maintain the stock, if a Desiro fails on the SWT network there's always another Desiro about to provide assistance to rescue the failed unit and as all drivers are trained to deal with both failures and assistance proceedures this doesn't really make sense?? even if a 455 or 458 fail they can currently assist each other.
Is this different on Southern and Network Rail assist the trains or will Network rail be like the AA for trains in the near future??
I mean like the hassle in the Portsmouth area this week, a Desiro decided to break down so another Desiro was sent to rescue it only for the fault on the initial Desiro to be transferred to the thunderbird Desiro - wouldn't it have been quicker for South West Trains upon learning that the second train had also failed for them to ask Network Rail if they could assist with a Class 57 if possible?
Network Rail do step in if required to recover a failed train and any associated costs get passed onto the responsible TOC/FOC, also other companies usually offer a loco and/or crew to help if they can.
It makes sense that they would but I didn't think they had stock locally that could assist, you learn somthing new every day