This may not be what you are looking for but I do have 2 gmail accounts on my phone and both are syncing to the calendar with no problem. Just add the second account and under the sync options you should be able to tell the phone which account to sync to the calendar.
go to settings, accounts.
Set up the second account.
Then go to the calendar app and under the settings there you can show which calendars are synched and shown,
Hope this helps,
M