Guest Blog by André Lussier - It is true that using the Mont-Royal tunnel for the REM could well forbid any other train to use it. The REM is a catenary driven electric train and its height is not easily compatible with bi-mode diesel electric locomotives already used through the said tunnel. See, both the most used line ( Deux-Montagnes North-West, already electric ) and the newest line ( 2 years old ) Mascouche (North-East, bi-mode locomotives) will be cut from the tunnel, defeating their usefulness. But the Deux-Montagnes line will be entirelty replaced by a new REM line rolling on the present day train tracks that have just been refurbished at a 400 millions $ cost. As for the Mascouche line, the REM offers a tranfer station to the REM somewhere on highway 40 ( I do not live in Montreal, so, some of my infos lack proper context, but I can read... ! ) to reach downtown, or any oth...