Default ITSPx DigitMap : (1xxxxxxxxxx|<1>[2-9]xxxxxxxxx|011xx.|xx.)
Rule 1 (1xxxxxxxxxx) and rule 2 (<1>[2-9]xxxxxxxxx) of the ITSPx DigitMaps are inconsistent. Rule 2 validates that the first digit of an area code is not a 0 or 1, but rule 1 does not. For consistency, both should validate or neither should validate.
Some VoIP providers (IdeaSIP for one) use numbers that look like US PSTN numbers with an area code of 0 or 1, so the default ITSPx DigitMap should be:
(1xxxxxxxxxx|<1>xxxxxxxxxx|011xx.|xx.)
This will provide compatibility with Google Voice and most VoIP providers.