From first-hand experience, B2B sellers do not get this information today. They typically get "signals" like "Company X is searching for product category Y" or "Company X is visiting your web site". And "Company X's CIO is John Smith - here's his phone number". But nobody that I've seen claims to offer individual names of web site visitors.
Services like retention.com provide email addresses for otherwise anonymous site visitors based on information provided to them by their "publisher network".
