It 'should' as it's a public road, but there's no legal obligation to cover it - Hence why many policies specifically exclude 'derestricted public toll roads'.

One option Dingy, is to call your insurance company and ask if they cover toll roads in Germany. When they say yes, get their name and the time and date of the phone call (insurers log every call). That way if you have an 'incident' you can quote the time of the call where they said you were covered.

Or pay separately for additional cover!