According to multiple reports (though possibly all based on one from 9to5 Mac), AppleCare representatives have been sent redemption codes allowing them to install Mountain Lion on their work Mac.
The OS is said to be the same build as the golden master released to developers earlier this month.
And TUAW notes that last year's release of 10.7 Lion occurred one day after Apple's third quarter earnings conference call, and the 2012 call is scheduled for later today (Tuesday US time).
Mountain Lion continues the trend of bringing iOS features to Apple's desktop OS.
It can only be used on relatively recent Macs, specifically iMac (Mid 2007 or newer), MacBook (Late 2008 Aluminium, or Early 2009 or newer), MacBook Pro (Mid/Late 2007 or newer), MacBook Air (Late 2008 or newer), Mac mini (Early 2009 or newer), Mac Pro (Early 2008 or newer), and Xserve (Early 2009).