The article about the Grand Avenue corridor in Arizona did not specifically say if they where looking at using the BNSF trackage or it would be adjacent trackage in the corridor. If they haven't talked to BNSF they are probably wasting alot of everybody's time and tax payers money.
That trackage is basically mostly industrial and is pretty busy. To build a new line there would probably require it to be elevated most of the way. because of all the street and railroad congestion.