(for clarity, I didn't mean to add a period between "significant" and "enough" in my message above).

I think if anything's really abandoned here, it's the railway (see railway=abandoned on the cycleway). Not sure of the history of the informal sidepath, but I see it as an extension of the bike corridor and thus covered by the single highway=cycleway. But I suppose it could be considered "optional micromapping" and if the side footpath is still vaguely there then it's fine to leave it. Perhaps tag as informal / review surface tags?