Is an erc20 token which is deployed on a private Ethereum blockchain of any value and is it possible? would it be smarter to deploy on another platform like fabric for permissioned/private blockchains?
Sure you can deploy it in your own network. Then it exists only within that network.
Tokens don't typically have value attached to them - value is only what the market thinks the value should be. And the token needs to be tradeable in some exchange to have value in relation to another asset (such as Ether or fiat).
It's rather difficult to say what would the the smartest thing for you to do - depends on your use cases.