Follow-up
So - finally received my invoice from AVIS. Sort of what I expected...
407 ETR Toll Charges
Toll: Hwy401 to Hwy400 on/le - $8.13
Video: Hwy401 to Hwy400 on/le - $3.80
Administration Fees - $17.00
HST on Admin Fees - $2.21
Grand Total (CAD): $31.14
I fully was aware this would occur - but it was well worth avoiding the 401.