Modern Treasury has now added support for Royal Bank of Canada commercial banking customers. Utilizing RBC's ACH Direct Payments & Deposits product, Modern Treasury is able to support the originating of Electronic Funds Transfer (EFT) credits and debits, with wire transfers soon to follow. 
In order to support EFT payments, Modern Treasury has made a few additions to the Create Payment Order endpoint, including the addition of the eft payment type and a purpose field corresponding to the 3-digit CPA code that will be attached to the payment. For customers who have EFT payments enabled, initiating a new payment is as simple as sending the following payload:
"originating_account_id": "<Internal Account ID>",
"receiving_account_id": "<External Account ID>"
Returns work similarily for EFT as they do for ACH and will alert you when EFT payments are rejected for any reason.
For more details on Canadian payment types, see https://www.payments.ca/resources/payments-glossary.