Read SharePoint files from PeopleCode (IB Handler)

Does anyone know of a way to read SharePoint files directly from w/in IB Handler code?

If users of a custom 3rd party system choose to upload files to Financials, I was imagining that the 3rd party system could just send reference to the file and I could make a FSCM attachment out of it.  I can read and make an attachment out of a network file given the UNC path (all Windows based), but I cannot seem to crack how to read SharePoint files.

The SharePoint files are in the format

http://dir1/dir2/dir3/document.pdf

I've tried performing a FileExists() against the absolute path in its