Scalix does NOT include the functionality of a BES.
You have 2 options.
1) Cheap - Redirect inbound email to a webmail Blackberry account. Then set up the desktop to sync your calendar and addressbook. This does work well, but You'll need to delete email in 2 places. You need to be using an older version of the Blackberry client or this will not work successfully.
2) Good -
www.notifycorp.com has a replacement for the BES. It provides similar services, except that it works with Scalix. It also works with devices that the BES doesn't, so you'll be able to use Treo's, Blackberries, and the PocketPC (or whatever) devices. It's reasonably expensive, and you need a MS server to run it on (or you can have them host it at their location.
Setting up #1 can be a challenge. If you need assistance, let me know.
Kev.