To reply to your question, I found a website all about icebergs, including how to tow one. The reply to that question is as follows;

"Towing icebergs was first demonstrated in 1971 in Newfoundland. It is now a common practice in the management of icebergs for the offshore oil industry. Towing may not be the best term however, as often massive icebergs are merely deflected slightly from their paths. The tow is arranged by a vessel navigating around a berg while paying out a floating tow line. A junction is made so that the berg is lasooed and then tow tension is applied carefully to avoid rolling the berg or pulling the line over the top."

Check out the whole site
http://www.wordplay.com/tourism/icebergs/