I can see why telecoms would have supported such a limit. If stricter rules were to be implemented for a 42V DC limit, it would have meant many expensive changes to the distribution systems in the average telephone exchange.
U.K. telecom power is nominally 50V rather than 48V, but even though a high battery voltage would just exceed the 50V ELV limit, the classifications were based on nominal levels rather than the highest which could actually be attained. (Similarly, the upper permissible limit for our nominally 240V supplies works out as 254.4V, but still classed as LV despite being 4.4V over the boundary.)
