That said, I guess you could certainly expose a service from the BizTalk server that wraps your policies and allows you to call them remotely in that way (this could even be a biztalk orchestration that calls the BRE exposed as a web service, for example).
Ik you make a remote service which talks to the BRE it is posible. In this service referense Microsoft.RuleEngine dll.
We implemented this solution in a project, so i can sau it is posible
If service is located on web server, Biztalk Framework should be installed on webserver to refer Microsoft.RuleEngine.dll.