The only RPI vacancies I've seen recently were with Mersey rail Electrics, (Rail House??)
With a little experience of "co-operating" with this TOC, I would suggest the jobs have already been allocated, regardless how you perform.
Sorry to be cynical, but Mersey Rail aren't seen as exactly a shining example of how to run a railway from other TOCs internal perspectives. One manager I work with described it as a "racket".
I think you may also find that there was a manager there several years ago that revealed that most of the RPIs had been being rather "liberal" with cash and company time... apparantly the ones that gave other names to the investigation got made managers despite being involved themselves! Some story if was true!
My role within 102 NS now involves a little bit of contact with 1 or 2 individuals in Mersey Rail, and they seem to completely disregard standard industry practices and procedures, so I suspect Mersey rail implement a serious number of Local Instructions or Standing Orders which nobody outside the company will be able to help you with. I am confident that they do their best to avoid any issues like the NRCOC...