You can use Physical link between VRs. Or import routes between routing instances.
https://www.juniper.net/documentation/en_US/junos15.1/topics/example/routing-table-import.html
https://kb.juniper.net/KB19787
https://www.juniper.net/documentation/en_US/junos15.1/topics/example/routing-table-import.html
https://kb.juniper.net/KB19787