Currently, we can only use Location's default number and assigned numbers from user's location. However, it was been noticed by various customers that it would be needed to use Hunt Group number solely, without having the need to make it main's location number.
Setting the hunt group number as the Main number is an option, though that also requires reconfiguration since the “advertised” number is assigned to an auto attendant and is the number desired to be the Caller ID number displayed for users. Setting that number as the main number reduces user configuration changes needed. Since hunt groups are a live answering point, it would seem to make sense to allow the use of these as an ECBN. After all, hunt groups are more likely to be answered than calls to an individual.