If you have your conventional mortgage with Scotiabank, you will have to switch the mortgage type to Scotia Total Equity Plan (STEP).
In order to do this, you will have to get an appraisal done. For example, if your house is appraised at $600,000 and your mortgage balance is $200,000, then they will give you a "Global borrowing limit" of $480,000 (80% LTV ratio of the appraised value).
$280,000 Available line of credit + $200,000 Mortgage balance = $480,000 Global limit
and YES, you will have to pay lawyer fees to discharge the conventional mortgage, and register the new STEP mortgage. Scotiabank also requires new title insurance for every mortgage, this will cost you another $100 - $150 on top of lawyer fees.
If you have good relationship with the bank, sometimes the will cover the appraisal fee up to a certain amount.
Cheers!