Yes it is possible. Use the Sql Express sync provider example ( http://archive.msdn.microsoft.com/sync/Release/ProjectReleases.aspx?ReleaseId=1200 ). It is not supported by Microsoft and uses Sync Framework 2.0 methods instead of the new Sync collaborative synchronization methods.
Enable change tracking on the server, create a binding table and a pointer on the client. Create synchronization adapters for each table in the synchronization agent, and you are turned off. You should keep in mind that the sql express service provider uses the server provider under the covers, so you need to cancel its thinking in some places (the download is loading).