What performance requirements are implied by the term "telecom applications"?
I know of at least one requirement for the telecom market and the DC-DC switching (or even linear) voltage regulators involved -  they need to handle +-48V on the input. This is quite high for modern voltage regulators in most of the industries/fields I've dealt with, and this high voltage is a remnant of the old days of telephone lines having to transmit signals over long distances, 48V was found to be useful for long range transmission and still relatively safe for humans in case someone touched it. 

At my university, 50VDC was the limit before it become illegal/very high risk/must be enclosed and never touched while live.

This is only a guess, but another "requirement" for telecoms grade regulators I could see as being important is high power supply rejection ratio (PSRR) on the regulators, low EMI (for modern EMI standards), and good line/load regulation (related in part to the PSRR). 

The "high speed" implies that a requirement for telecoms power regulation is that the regulator topology has fast transient response, meaning multi-phase DC-DC converters (synchronous buck converters, for example) or high frequency converters for faster and tighter control over the load.