They were originally a GCP wrapper but they started colo'ing their own racks about a year ago.

https://blog.railway.com/p/data-center-build-part-one

I think it has it's own "metal" services they're migrating customers to. Afaik they used GCP for "legacy" cloud services.

All of these services are bundling the underlying AWS/GCP/etc resources in an easier to use package.