I wouldn't get hung-up and throw a hissy over the mention of a 48 port thingy ..... this may be for trials, who knows ??
It is indeed a temporary limitation for the current trials.
The main cause is that, right now, chipset companies can't put together the silicon that can run 96 lines - which is BT's apparent ultimate target.
It isn't the plain "running" of a line (or 96 of them together) that is the problem. It is the work needed to get the vectoring process to successfully use data for 96 lines in parallel.
Sckipio shows this most publicly, and
had this to say 3 months ago. Slide 4 shows "vectoring for 16 lines shipping in 2015; vectoring for 24 lines shipping in early 2016; vectoring for 32 lines in demo form". Huawei appear to say they'll have 96-port units available at the end of the year ... so definitely not in time for the pilots.
a solution to use a 48 port G.FAST MA5818 chassis unit
Googling suggests that the MA5818 is a chassis of the same size and appearance as the MA5616 appearing in All-in-one cabinets. It has room for 4 service cards, a power card, and control/backhaul card, and a fan card. The 5616 DSLAM can be seen in
this all-in-one cabinet, as just the small cream-coloured part. An example of a 5818
can be seen here.
It looks like the 5800 series DSLAMs are aimed at the NG-PON (10G PON) backhaul market, so are likely have an increase in backplane switching speeds compared to the 5600 series. The next generation of hardware, I guess.
a) a PCP side pod, or
b) in a standalone G.FAST cabinet, or
c) in the existing NGA DSLAM cabinets
Really good to see the options being kept open.