Simple answer no. They will not activate it in a receiver that is not owned by them. Most FTA receivers card slots are for different encryption formats than what Dish Network uses. (I know that the Pansat 3500 is for Conax (Used in Europe))
It depends on the speed of the receiver and the settings (If applicable). (Detailed scan vs. Fast Scan) Also some receivers like the Coolsat 5000 or 6000 can blind search all the satellites with one command, but with the Pansat 3500 the user must scan each satellite individually, so if you leave the FTA receiver it will wait until you get back to tell it what to do .