Bombardier Shares Dive as CEO Quits  MONTREAL (Reuters) - Paul Tellier stepped down as president  and chief executive of Bombardier Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BBDsvb.TO target=/stocks/quickinfo/fullquote"&gt;BBDsvb.TO&lt;/A&gt;  on Monday,  surprising investors and sending the train and plane maker's  shares down as much as 26 percent to a 10-year low.