Not always it probably depends on the size of the operation, I did a stint in a call centre for a few weeks and they gave us lists that they bought and split between us to work through. I think there must be lots of people selling lists that are years old because every single list would have loads of people saying they were on the TPS, sometimes said person was deceased etc. If you tell them you are on the TPS and you demand they take your number off their "database"(they might not have one and just add it to a list of numbers not to call in future, there will still be someone selling old lists about to other companies though) then they will do it to cover their backs.
Still these smart phones seem a good idea, it will cut them down drastically I'd imagine, until they find a way around it.