Let me know if you've run across any info about this.
I'm not aware of any clearinghouses for this kind of information. I'd recommend working through the MCP Magazine (www.mcpmag.com) Web site, and researching the various offerings there as the next best thing to a "who guarantees passing scores?" compendium. Interesting though your question is, I'm not aware of anyone or any site that provides a general answer to that question for all known certification-training providers. Sorry I couldn't be of more help.
This was first published in October 2002