I've not ever looked at SCCM. However, the topic of silent installs has come up a number of times in the past - there are a few postings on the old forum. The package has essentially 3 parts - 1) some application files, that you could copy basically anywhere on the users' machines; 2) some registry settings that point to there - these are per user in the installer but with Office 2010, it's possible to load add-ins from the machine hive, which would probably help you. 3) The other component is a bunch of prerequisites, such as the VSTO runtime (I don't have it to hand at the moment, but there's a list in the readme file from the download zip) - you'd have to check what each of these say about silent installs/SCCM since I have no control over those at all.
Within the zip, there's an "application files" directory - that is the complete set of files mentioned in point (1) above. To see what the registry settings are, install the package on some machine and have a look in HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addin\NoReplyAllAddin - note that the file path would need to be updated to point to wherever you store the files from (1).
If you do try this, please let us know how you got on - perhaps this is something we can consider for a future release mechanism.
- Proposed as answer by Gavin SmythMicrosoft employee, Owner Friday, August 05, 2011 3:48 PM