Accesing the mgmt resource or mgmt IP from a non-common partition

I guess you mean a route domain rather than partition. If you have strict isolation between your route domains then the only way that you can provide access to network resources on route domain 0 is to make RD0 the parent of the route domain in question. The purpose of this is to allow access to common components from each route domain.

You could also use an external router/firewall to provide the routing.