I'd guess not--they already have to keep track of the channel mapping, (which likely is outsourced (Tribune?)). I doubt they'd want to keep track of every channel package offered by every provider. The only exception (again a guess) might be if you were using a Dish-branded Sling Adapter or a Dish Slingloaded DVR. Dish (who owns Sling, Inc.) may have optimized things to the point where the guide provided by Dish-branded Sling hardware might reflect the channel lineup on one's Dish package.
Otherwise you may need to use the guide on the Dish receiver itself, rather than Sling's built-in guide.