I was successful in getting a conditional status match/challenge to Platinum at Marriott by using the "Contact Us" feature on the website. I had initially called and the best they could do was a 6 night challenge to Silver.

I sent an e-mail stating that I was Platinum with Starwood, and will be visiting a new location which will require me to change my business to either Hilton or Marriott. I pointed out that I had prebooked my next 5 weeks worth of stays with them, trusting that they would take care of me. I also guaranteed them a minimum of 130 nights/year of business and offered to send them all of my past history with Starwood.

Within a few hours I received a response that I was immediately upgraded to Platinum and needed 18 nights in the next 3 months to maintain that status. Keep in mind this is over the holiday season, so it might have been a longer period then normal. I also think it helped that I sent it from my corporate address, which Marriott has a very strong relationship with.