We should be able to reference custom fields associated to a Typeahead object through Calculated Custom Fields and Calculated Columns.
valuefield=[Typeahead Field Name]:[Custom Field]
Ex. My organization uses a User Custom Form to track employee details such as 'Department' or 'Employee Number'. When a request is submitted on behalf of another employee we would like to use the Typeahead field to identify the employee and then have a set of calculated custom fields to 'auto fill' in the rest of the employee details.