Electricity too cheap to meter
More power consumed in summer to help it keep cool in Australia.
Other than that, the power draw is fairly constant. 384 lines per node cabinet (ex last year's blurb). Single-digit watts per line. Likely less than $1/month in electricity cost per line. (Telstra gets $9/month for an ULL.)
Getting power from the numerous end-points to operate the node is not as silly an idea as grid-connected PV solar.
Power protection is simple and the power domain easily restricted to individual lines at a primary level, to the boards for the multiple lines at a secondary level and finally to bleed off a little from each of the hundreds for any central functions inside the node cabinet. The bulk of the necessary primary protection circuit is already required to handle surges due to e.g. lightning strikes and accidental connection to the mains grid. The failure of one customer's modem would have no significant effect on operations. The vast majority would have to fail affect the lines of other consumers.
The technical impediment is that the core design of the circuits inside the cabinet is for power originating from one source being divided to service many lines.
The loss of utility is the same as with FTTP; no power from the subscriber end and there's not even a basic phone servce; unless the node has a UPS and can drive the lines in POTS-fallback mode. That requires more complex cicuitry.