There are up to 15 new cost fields available for each IC item, depending on how many you define in the Inventory Company Profile. Enough for one per province.
Then define the Base in the OE Tax Table as the specific new cost field.
You probably will want to create a different OE tax table for each province.

A demonstration of setting up the items for this type of environmental levy is shown in the webinar for the Adagio Inventory 8.1C upgrade, starting around the 17:30 mark of the video.