I've a feeling that you won't be able to get Infinity from that distance, I'm 0.8miles by road from my cab and the checker doesn't say anything about infinity. I then checked a few of my neighbours numbers, one of which I could throw a stone at and they get an estimated speed of 16meg on BT infinity. Looks like I'm stuck with 0.5meg 
Why? You can get ADSL miles from the exchange. You could certainly get a working VDSL connection (for infinity) at similar distances but obviously the speed decreases back towards ADSL speeds as the distance increases. Point is, at lesser distances, which is why the cabinets are installed in local neighbourhoods, you usually end up with a higher speed than was previously attainable with ADSL services.
As for your own circumstance...the checkers update as the work to install cabinets and associated infrastructure completes. Also note that your neighbour isn't necessarily on the same cabinet as you regardless of how close they are to you.
---
BT Infinity 8th July 2010
Connected to: P23 10 KILMAINE ROAD BT19 6DT
600m to cabinet
25.5mbit down / 7.6mbit up
Previously:
BT Broadband, roughly 4mbit sync
4KM line / 54dB atten / 9dB SNR / Netgear DG834GT