I dont know about a 'Blackspot map' but each company has a coverage map.
I know where I live is in an unmarked area for automatic activation which meant I have to go the 'Black Spot' declaration but I suggest you read both C7 and Impaja websites as they both gave me the impression they dont want new customers.
Good luck as I will be VERY interested to see such a map too.
As far as the ABC/SBS goes, they will activate a card if you live in the South Tower of the Sydney Harbour Bridge.
Bookmarks