text: Bombardier CEO Quits, Shares Plunge  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; &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BBDb.TO target=/stocks/quickinfo/fullquote"&gt;BBDb.TO&lt;/A&gt;,  sending the train and plane maker's shares down as much as 26  percent to a 10-year low on Monday.