You can clone with
This code should be able to take a URI and 1) determine if it is a playlist based on basic extension matching 2) parse / expand it to a list of tracks and/or playlist instance.
As for playlist types we should consider supporting the current list is M3U(8), PLS, ASF, ASX, RAM and XSPF. When it comes to actual use in the backends the idea is that we check for a playlist match in the lookup method of the library, and if we match fetch, parse and expand the playlist returning the tracks instead.
python-totem-plparser and/or gir1.2-totem-plparser-1.0 could probably be used for the heavy lifting. Other idea I've been considering today is if we could create a typefind element that identifies playlists, which would ensure a playlist bin gets autoplugged which could parse and expose the actual media file to downstream elements.
http://cgit.freedesktop.org/gstreamer/gst-python/tree/testsuite/test_typefind.py has example code for creating python based typefind code (also note that this testsuite also has a bunch of other useful examples).