For dedicated they say this:

>All root servers have a dedicated 1 GBit uplink by default and with it unlimited traffic.

>Inclusive monthly traffic for servers with 10G uplink is 20TB. There is no bandwidth limitation. We will charge € 1/TB for overusage.

So it sounds like it depends. I have used them for (I'm guessing) 20 years and have never had a network problem with them or a surprise charge. Of course I mostly worked in the low double digit terabytes. But have had servers with them that handled millions of requests per day with zero problems.