Can he import his BCH recieving address on a BTC wallet and access it?
Yes.
More specifically, Bitmain can import into a BTC wallet the private key that is associated with the BCH receiving address. If they do that, then the BTC wallet will generate the same address from that private key and will be able to access the bitcoins that were sent to that address.
That's what I said above, the private keys are the same on both chains.