Interoperability via generic protocols such as Interledger is being investigated currently, and may require some extensions to the core platform to support, depending on the approach used. Bespoke CorDapp contracts that support connectors and escrow accounts as called for in the Interledger protocol (Universal Mode). For Atomic mode, where a co-ordinating notary is required, there would be further development required to support external notaries. Such notaries and their particular consensus methods would need to be separately developed and integrated.
Did you have a specific use-case in mind?