Seems that the subscription/filter needs to be setup before messages are sent to the topic. I tested this by creating a topic and a subscription. I then posted messages to the topic with property DriverID. I passed in a DriverID = 1. This message ended up in the subscription setup earlier as this subscription has the 'MatchAll' filter by default.
I then created another subscription with a filter of DriverID = 1. When I posted a message to the topic and set the property DriverId = 1 it got sent to the 2 subscriptions as expected. Messages posted before this subscription was setup that had DriverID = 1 were not automatically moved to the new subscription that matches the filter.
Paul