It shouldn't be long after it's put in until the checkers show it as available for orders...a matter of weeks.
This assumes the work is complete. Often a cabinet can look finished from the outside and then you'll find workers back a few weeks later adding more to it.
It's not in anyones interest to install new kit and then have it sitting idle longer than necessary.
BT Infinity 8th July 2010
Connected to: P23 Kilmaine Road, Bangor, BT19 6DT (NIBA
600m (approx) to cabinet
25.5mbit down / 7.6mbit up
BT Broadband, roughly 4mbit sync
4KM line / 54dB atten / 9dB SNR / Netgear DG834GT