(could one of the moderators move this to... um... Midwest Railfan maybe? Maybe there's already a thread on the DM&E?)
Yup, you're right, it is speculation that they'd buy the DM&E, though it started with someone else on this forum. If I can find the post, I'll link it here. Not sure that anyone would like to buy them right now - the UP appears to be kind of P.O.'d at them if the site below is to be believed. They apparently skipped out on $591k payable to UP for environmental remediation.
http://www.dmetraintruth.com/ (the site does have an axe to grind though)
The site also hints that the DM&E is foreign-owned, though they don't support that assertion. It certainly is privately-held though, so maybe Warren Buffett did buy a slice.