It will be to any FTTC cabinet in time, but the word is that a limited availability as Openreach train up more engineers and then a wider coverage.
FTTC fibre twin - I mean the cabinet with the air vents housing the FTTC hardware, next door to the older telephone cabinet. The Aggregation Node will usually be fairly close to the new cabinet.
13 Mbps estimate suggests a distance more like 1km rather than 300m. So how sure are you the number of the cabinet you have seen corresponds to the one your telephone connects to.