Just to update on this – I have spoken to Google Apps for business and this behaviour is expected with their current technology and Outlook 2010.
There is a workaround which I have copied and pasted below – it involves saving the appointment as an iCalendar file to your hard drive and then attaching the saved icalendar file to the invite before sending on.
The end user receives the email with an icalendar appointment attached – they double click on that and save the appointment so it adds to their calendar WITH the attachment viewable from the appointment.
It isn’t perfect as the calendar file doesn’t always offer the option to send an acceptance to the meeting but you can save it to your calendar.
Google Apps workaround copied and pasted below:
Here are the full details of the work-around we discussed:
1. Create a meeting with attachment
2. From the ‘File..’ menu, choose ‘Save As’ and choose the format to be iCalendar (.ics) file
3. Attach the saved .ics file to the meeting
4. Send the meeting invites
5. Invitees receive the email with both attachments
6. Double-click on the .ics attachment in the received email to accept or reject.
For More Details: http://www.recoverdatasoftware.com/convert-ost-to-pst