The "free" phone conference service work in a somewhat similar way. There's a fee charged for long distance call even in the US/Canada. The fee is low enough that most people now get free long distance.

The free phone conference services are terminated at tiny little telcos that charge a much higher than normal fee for a north american long distance and the fee is split between the conference service operator and the telco (which may or may not be the same.)

Some of these services cannot be dialed via some VOIP providers (like Google Talk) for that reason.