Always meet the criteria of the application, then tailor your information for the role. If there was a request for a Referee then it should have been provided. It is well known (at least on this forum) that the smallest thing on your application can let you down. The railway is in a position where they can pick and choose at will and be very very picky about it. When I was recruiting (back in a previous life) If I had put out an advert and requested references and the applicant didn't provide them, or stated they would be available when needed, I would think they were hiding something. I would also think that it was a failure on the applicants part that they didn't provide information that was requested.
When I had a bulk load of applications, the first thing I always did was bin anyone who didn't meet the basic criteria requested. Another prime example with rail recruitment is the distance from depot. If the TOC wants 10 miles then ensure you are within that. Granted people state they are willing to relocate but if I had applicants that were already meeting that criteria then they would be higher up the list.
Maybe a few years ago being a Copper was an advantage as less applicants were coming from that field. Now there seems to be an abundance, giving the TOC the ability to cherry pick.
Personally I think the initial sift is the hardest to get through; especially as feedback is rarely provided. It is very hard to stand out during the initial sift and the move towards online applications, I believe, is making it harder because the tiniest thing will make the computer reject an application.
What you may also need to do has already been highlighted. Tailor your information to the role applied for. Conductors are very customer service based so push that. Drivers are safety based so lean towards that.
Never rest on your laurels and assume your going to get a role. There are hundreds applying for a role so you are a tiny fish in a very big pond. There are other applicants with equal or greater skills that you. You may be perfect for the role but a small thing may had tipped the balance to another applicant.
Most importantly, NEVER give up. Plenty of people get knocked back and as we never really know why that was they tend to get downhearted and have a feeling of failure. It may have been a simple thing like the references or something beyond your control and they simply reached too many applications so pulled the recruitment for a bit. I was knocked back and it transpired that the TOC I applied for had just lost a huge contract so pulled all recruitment. I got a generic rejection letter. I just keep applying and pushing harder till I got the job.
They haven't said you can't apply in the future and they haven't said you need to wait 6 months. So take that as a positive and reapply at the next opportunity. Also, maybe take a different route. Get a different role at that TOC and wait till something comes up internally. Build up your skills etc.
Whatever happens and whatever you decide, good luck with it all.