if you're trainsiting over someones ATZ at 2200 feet technically you're 'outside controlled airspace' but it would be rather daft not to give them a call.
I guess there is always an optional area of cover near any border. Mainly this is used to mitigate the risk of an airspace violation as well as providing you with any relevant traffic advisories.
You will not be seen in a positive light if you bust and you're totally not on frequency.
