as far as telephone lines are concerned is a surge resulting from a lightning strike - what engineers call a "good hit". Switching transients generally do not occur on telephone lines because no powerful inductive devices are connected to the phone system. If they were, your phone wouldn't work.
Power spikes from lightning strikes are certainly a danger, and anyone with a modem or ADSL router connected to a phone line will be well advised to pull the connector jack from the microfilter when storms are in the vicinity.
You can buy telephone line surge suppressors, but they must be connected to an external earth - preferably the same one as your computer - so as to avoid potential voltage differences between the surge protector and your computer.
click here to see a range of available devices.