Well, my purpose isn't to argue with you :-) I'm simply reporting my findings based on a pristine user account I maintain strictly for the purpose of verifying default settings & Preferences. In 2008, 2011 & the beta, neither of the shortcuts you mentioned
originally nor the Ctrl+Command+0 combination are used for any command in either version. I'm not doubting what you report, but assuming you're right it has to be due to someone or
something* having assigned it at one time or another. [*Add-ins such as MathType often bring their own keyboard shortcuts along with them, but at this point add-ins aren't supported in the beta software.]
The built-in keyboard shortcut to insert an equation in Word 2011 is Control+=, which also works in the beta. [Actually, the keystroke is assigned to the
EquationToggle command, but it actually serves to insert a new equation.]
If you want to create a custom keystroke, use the instructions in Word Help on the subject:
Create
or delete a keyboard shortcut
The procedure in the beta is the same as in Word 2011. Select All Commands from the
Categories list, then assign the custom shortcut to either the EquationToggle or the EquationInsert (not InsertEquation) command.
Footnote: I sincerely hope you aren't relying on the beta software for meaningful work :-)