To start with, interoperability between blockchain is possible to some extent. For example, the smart-contracts of Ethereum do work on Monax.
From what I know, stream concept of multichain is just a data retrieval mechanism. You can store data on all the platforms you mentioned but they are not optimised. For example, it takes 10ms to read data value of a key in a stream in multichain. If you do the same with monax(now part of hyperledger), you need 1000ms.
Stream concept is unique to multichain but its data storing aspect is not new. In future if you want to make communication between 2 different blockchains, e.g., Monax and Multichain, you need to develop a secure bridge which is counter intuitive to blockchain's core concept of decentralisation.
However, if you are more interested in blockchain as a database, you can look at https://www.bigchaindb.com/
This project is a like a database with added features of a blockchain and not a pure blockchain.