XPO does not track changes made in the database. A possible workaround is to use the feature described in this blog: XPO Beta feature: SqlDependency support.
XPO does not expose SqlDependency notifications, so there is no way to track the exact moment when the changes were made. You can simply repeat queries in a small time interval. For example, execute the XPCollection.Reload method on every 1000th millisecond.
This will not impact the application performance, because XPO will return data from cache, without performing actual query to the SQL Server. However, when another user updates data, the query will be performed to update the cache. So, the data in the client application will always be up to date.