The simple answer is that none of us really know.
The new services have specific caps assigned to them, that is clear from the announcements.
We also know that ntl have plans for metered access next year - this is in their own presentation document, so they must be installing equipment to monitor your usage.
The existing services also have a limit, that is not applied much at the moment because they don't have the means to monitor and enforce it.
Put these facts together and what do you get ?
The implication is that as soon as ntl has the means to monitor your usage properly and individually, they will. What will happen if you then exceed your limit - again, no one knows, but an educated guess would be that you will have a choice of either paying for extra, or being dropped right down in speed (probably to 150k). I do not think they will ever cut people off.
I believe that by this time next year - all the ntl services will be limited, and the limits enforced. Only time will tell.
