He did say phone interview. I think it's fine to ask about salary during communication prior to an in person interview, whether it's over the phone or through e-mail. Why spend time and money to go to an interview and then find out the salary is not what you thought it would be . Waste of time for both parties.
I guess it's tough if this is your first job out of residency/fellowship because you're not sure what you might be worth. But I think when you've been practicing for a few years and know what the market is, it's easier to know what you're worth and what to look and ask for.