Hate to burst everyone's bubble but the gas you fill your car up with, regardless of the brand, is pulled from the same storage tanks.
I work for a firm that, amongst other things, owns 22 C-stores, mostly Citgo (which we are in the process of unbranding simply because the CEO's are fed up with Chavez & his non-stop mouth & the bad PR he brings to the Citgo brand) & Mobil. All of our gas is pulled from either Green Bay or Junction City (pop. 200) & comes up to this area via one pipeline out of Chicago. Via some bizarre allocation method (of which I have no idea how it works) each "brand" is alloted volume to push their product up the line to the tanks squatting in the aforementioned locations. BUT, whether I fill up with Citgo or Mobil or BP or fill-in-the-blank it's all pulled from the same tanks.
From the way it sounds Top Tier is more of a marketing idea than an actual type of gasoline. I suppose it would work the same way any other campaign is run: "brand" something, convince manufacturers to help "sell" it by giving them publicity or actual dollars (who knows?) & voila', Top Tier gas!
By the way, gas went up 12 cents this morning around here (once again, who knows why?), $3.34 for premium.