[tialaramex]

You can see some statistics for Comodo's crt.sh monitor here:

https://crt.sh/monitored-logs

Note that this doesn't tell you whether a CA logs all/ most or none of the certificates they issue. In my experience it would be unusual for a CA to deliberately _wait_ before logging certificates, either they're logged more or less immediately or they don't intend to log them at all. To issue certificates with an SCT baked inside them (which is convenient for customers) you have to log a "pre-certificate" with the exact same details first anyway to get the SCT.

BUT if there's a problem the Mozilla trust store policy (and perhaps others, but only Mozilla's happens in public where we can see it) says the CA must show the trust store all the affected certificates. By far the easiest way to do that in 2017 is shove them all into a CT log and then spew a list of links to crt.sh or another monitor, rather than uploading some Word document full of X.509 PEM files or whatever. So even CAs that we know don't normally log everything will put all the problematic stuff into logs during disclosure, or else someone reading m.d.s.policy will do it for them.

Some CAs have a deliberate customer policy of letting you choose NOT to log, sometimes with a warning saying if you don't log this stuff then Google might distrust it. Symantec was really into redaction, which is logging but with the "sensitive" bits of the certificate removed. But Google never really bought that idea, and Symantec are exiting the CA business.