After some amount of poking around, I've found exactly one case where that happened (https://en.wikipedia.org/wiki/Lavabit in connection with Snowden).
Law enforcement might subpoena, say, search result records in connection with a specific crime (certain keywords + location + timeframe), but larger companies with the resources would absolutely have the ability and incentive to fight something as overly broad as requesting SSL keys.
Law enforcement might subpoena, say, search result records in connection with a specific crime (certain keywords + location + timeframe), but larger companies with the resources would absolutely have the ability and incentive to fight something as overly broad as requesting SSL keys.