My assumption is that the AIO cabinet is capable of servicing 128 fibre circuits - is this correct?
They can do up to 256 circuits with 4 x 64 port line cards.
The All In One cabinets contain a Huawei MA5616 DSLAM. It's the same DSLAM that's used in the small single door Huawei cabinets.
Since OpenReach started deploying these the maximum number of ports on the line cards has grown from 24 to 32 to 48 and now 64 port cards are available and regularly used.
Some of these DSLAM's have 4 x 24 port cards (96 total) and others have 4 x 64 port (256 total).
What's installed depends on how many properties the cabinet covers and the expected take up rates.
It's common that only a single card is installed when the cabinet is initially commissioned/activated.
I would trust the advise that the cabinet needs additional line card(s).
Edit: as above a 2nd line won't help. If VDSL2/FTTC cannot be ordered by anyone on the cabinet then the same will apply to any 2nd line you order.
You can test this by attempting to place an order for a new line. FTTC will not be an option during the order process.
Edited by j0hn83 (Sat 13-Feb-21 16:37:47)