Referencing files from one Blot site on another

I have a Blot site that operates my blog on a custom apex domain, and a second Blot site for photos at a subdomain of the same address. (This is because I have a fork of the Blog theme for the former, but prefer the Portfolio theme for the latter.)

If I sometimes want to include photographs inline on the blog, is it OK to reference the files at their URLs on the subdomain? If that’s going to cross wires for Blot, I’ll upload a second copy to the blog’s folder.