PhoneBurner allows multiple ways to distribute leads, one of which is a Blind/Preview Pull.
Blind/Preview Pull LeadStreams prioritize the newest uncalled contacts first. Then, after all contacts have been called, contacts are distributed based on the last call date. (The list is sorted by the longest period of time since the last call. So if the contact has been called recently, the contact will be one of the last to contacts to be distributed.)
For example, if a CSV file with 1000 contacts is imported today and your team calls through 500 contacts on that list, and then tomorrow another 1000 contacts are added, PhoneBurner will call the newest 1000 contacts before it will start calling through the older 500 contacts. Those contacts with the oldest Last Call date will be dialed first before those contacts with a more recent Last Call date.