Yes, they note that they use bitpay on the website:

> Our new Bitcoin integration is available through BitPay and can be used alongside other payment services, like Shopify Payments and PayPal.

But they don't mention whether there are any service fees added by Shopify

We treat Bitpay transactions the same as any other in terms of fees/pricing. There's a 1% or 2% transaction fee on plans with lower monthly fees, but those are waived if you use Shopify Payments for credit card acceptance (even on Bitpay transactions).

A better breakdown can be found here: http://www.shopify.com/pricing

That would be something useful to note on the website