Most people in the Toronto area DO NOT work downtown. Although the DRL is needed to deal with expansion in downtown employment, most employment is in the burbs. If the Eglinton LRT is overcrowded with people going crosstown, then we will be forced to waste money ripping it up 20 years from now and replacing it with a subway and the DRL will be useless for this purpose.
Do we really think that we can meaningfully improve crosstown commutes using low capacity tram lines? Using the 401 as an example, the LRT might have enough capacity to handle people using the express lanes, but if all the people using the collector lanes use it as well than it will be totally and completely overwhelmed. Add in all the drivers on Sheppard, Eglinton, Lawrence, York Mills, Finch etc. and all the users of overcrowded buses running along those roads and you get way more people than a slow/low capacity streetcar line can handle. The only way to fix traffic congestion in the suburbs is to build a network of subways, elevated subways, and high frequency commuter trains, and connect them to all the major suburban employment areas (e.g. Airport Corporate Centre, Pearson Airport, Eglinton/Yonge, North York Centre, Eglinton/DVP, Consumers Rd., Leslie/7, Scarborough Centre).