Manually move iCal into Lion
The best chance of success it to make a new user account and try syncing the phone to the new empty calendar. Just sync the iCal data. 

Then back up the lion iCal data to one file in /Users/Shared and import that to your proper account. 

Should that fail, trash that temporary user account and make another temporary admin account. 


Turn off time machine ( to prevent an automatic backup slowing things down )
Set lion to back up to your snow leopard time machine ( stop any backup if it commences)
Start iCal
Browse backups from the iCal menu
Restore your calendars one by one
Back up calendar data to /Users/Shared
Set Time Machine to your preferred destination and clean up the temporary user.