Last weekend's experiment to implement my own script to contact MT XML-RPC server resulted in success with the help of this post as well as with an anatomy of XMLRPCServer.pm in MT distribution. The experiment was to post an article from my desktop computer triggered by Perl script that I prepared. Frontier-RPC Perl module facilitated the script preparation by simple API.A code excerpt here will give you an insight how you can call MT XML-RPC methods prepared and exposed for you. Update for this code will available at the same link whenever available. Hope it helps.
Posting articles to Movable Type blog by self made Perl script using XML-RPC
Movable Type (MT) exposes interfaces to communicate with external services in exchange of actions and/or data with XML-RPC facility.
Blog posts saying XML-RPC in Flickr and Windows Live Writer made me experience how it works remotely and independently from MT dash board.