And by escrow you mean the CTIP as described in the Bip right ?
If not then you are not talking about bip300 and drivechain.
The ctip is an aggregation of all the UTXO's sent to the sidechain and held for future withdraws. Miners have nothing to do with it, its state or amount.
If miners can split and steal from it, they can seal from any other bitcoiner.