Not to my knowledge, but there is a general standard emerging on how to upload files to an object. It has been written by Matthew G. for contacts and you can find the code in HEAD under /packages/contact/www/files*
Just exchange party_id with bug_id and you are set to go.
In the long run this functionality could hopefully be an include in acs-subsite (as neither acs-kernel nor acs-tcl have includes) and be reused to attach files to any object (currently we are copying the code manually to all the packages where we need it).
