Your question makes the assumption that all full cabinets gets capacity added. That is not always the case.
If a cabinet serves 300 premises and a 288 Huawei fills up then they may not feel it is justified to pay for an extension for such few properties.
I know many cabinets at capacity that have had a waiting list for a year or 2 and still have no plans to be expanded or have a 2nd cabinet fitted.
I know other cabinets that have had extensions/2nd cabinets added before they even reached capacity and have never had a waiting list showing.
To answer your question though it can take many months to add a 2nd FTTC cab.
A High Density upgrade can be done I a matter of weeks in some cases.
Usually both take months of planning though.
There's a lot more work involved in adding a whole new FTTC cab compared to an HD expansion.
Important to add that existing ECI cabinets that reach full capacity can't be expanded and would need a 2nd Huawei cabinet placed next to it.
Edited by j0hn83 (Tue 14-Aug-18 13:08:56)