I have not seen a topographical survey of the area, but a casual review of the study area on the websites suggest that the only "dry" approach from Greenville to the Dallas area is a narrow piece of high and dry land between Lake Ray Hubbard and Lake Lavon. Of course, this area is served by the very busy and well traveled hwys #78 and #544. The right-a-way purchasing and traffic congestion caused by a new tollway entering this area would be at least dramatic. On the other hand, Rowlett is no bargain. In order to pass thru the Northshore area, it would require a bridge over Lake Ray Hubbard and build a bridge or elevate the roadway as it passes thru a long and very low lying area in Northshore.
As long time readers of this blog knows, I think the Northshore area has been horribly mis-diagnosed as a place for office and warehouse development. Adding another tollway doesn't help the warehouse and office market. It still costs money for employees to get to work and tolls for rolling stock (trucks) of the warehouse business. However, a new tollway should add sufficient re-thinking to knock Northshore off dead center for future development. Overall, the Blackland tollway would be good for Rowlett.