Given that the actual fibre line is blown through basically a small diameter black tube, I suggest that the latter's entry and possible exit to the next FTTC cover two of the small, black tubes, with the Mains Electricity Supply taking up the third small tube.
Also the fibre and mains are mainly employed at one end of "my" Huawei FTTC, it seems likely that they would be grouped together, at the DSLAM/Mains/Back-up Batteries end of the FTTC, generally apparently the left-hand side as viewed in the open doors.
The "bent-over" small tube with an apparently yellow stripe seems likely to be the end of a fibre conduit/duct, coming in to the FTCC, waiting for the actual fibre to be blown through it.
The much larger grey tube is probably for the multiple copper links to and from the associated, traditional PCP, from which the existing D-Side lines to the houses etc spread out.
In the case of "my" FTTC, it can handle up to 288 Subscriber Connections, with two wires IN and two wires OUT
That is, 4 Wires times 288 Subscriber Connections, thus requiring 1152 wires, to pass between the FTTC and the PCP.
These are terminated on the back-plane with 288 sockets, in to which Filter Links are progressively plugged in batches.
In "my" FTTC when first activated, only the first 48 sockets had those Links plugged in, March 2014.
Another 48 were added in June 2015, as I spoke with the technician doing the work, taking about 5 minutes. He had about 20 FTTCs to do that day, so it appears to be the normal progression. I am not aware of any more being added since then.
Taking the typical size/diameter of phone wires, the grey tube appears to be the only one capable of accomodating such quantities of wires.