I can't answer to your question, but for your information OSX does allow to use ":s" or "/s" in the name of the file. Specifically: you can enter a "/" in the Mac-path of a file (for instance, in Finder, or in a colon-separated path in AppleScript.) The underlying UNIX system will convert that "/" into ":" - a casual character for UNIX. You cannot enter a ":" in a Mac-path, like you cannot enter a "/" in a UNIX path.
Look:
tell application "Finder" to set x to selection as alias
-- alias "emmanuel's hd30:Users:emmanuel:Desktop:test/file"
POSIX path of x
-- "/Users/emmanuel/Desktop/test:file"
Emmanuel