Are any fees still charged during the waived monthly chequing fee period?

Yes. Monthly package fees are waived, but standard service fees still apply if you exceed the monthly transaction limits. 
For example, the Promotional Classic Chequing account includes 10 free Interac e-Transfers^® per month. If you send more than 10 in a month, standard transaction fees will apply to those additional Interac e-Transfers^®.