Just tried this, all worked fine. For Approve/Deny template I had this -
[event:signupusername] The event/enrollment for Event: [event:title] on [NOTALLDAYEVENT][event:startdate][/NOTALLDAYEVENT][ALLDAYEVENT][event:startdate|D][/ALLDAYEVENT] to [DISPLAYENDDATE][NOTALLDAYEVENT][event:enddate][/NOTALLDAYEVENT][ALLDAYEVENT][event:enddate|D][/ALLDAYEVENT][/DISPLAYENDDATE] ([event:timezone]) - [event:recurring] - has been updated
Which for an approved enrollment has this suffix -
- Enrollment for user [event:signupusername] has been approved
I got this email -
SuperUser Account The event/enrollment for Event: Test on 25 October 2009 07:30 to 25 October 2009 08:00 () - 
Every 1 week(s) on: Sunday until 01/11/2009 (Total 5 Events) - has been updated- Enrollment for user SuperUser Account has been approved
lastupdatedate is when the event is last updated. An event enrolment doesn't change the event record, which is what that date shows, it adds a signup record. I can be sure that if we updated the date whenever someone enrolls, someone will complain that the date shouldn't be updated, because the event details have not changed, and it would start messing with RSS feeds and the like. We could add a separate token for the date when the user tried to signup, if you would like to request that on Gemini 
.
Cheers
Roger