My guess is they looked at latest pension statements and found what their pensions would pay if they stopped working now, then they used an annuity calculator to find out how much money one would need in an annuity to earn that much. 

https://www1.rbcinsurance.com/cgi-bin/rbaccess/rbunxcgi?F7=SF&F6=1&7AWSREQ=1&F21=PB&F22=YVL7APTSrv.HTTPPassthrough&7ASERVER=YVI0&7ASCRIPT=%2FYVI0%2FPOA%5CGettingStarted.aspx&7APROTOCOL=HTTPS&7ALANGUAGE=EN&LANGUAGE=E

Funny though, they never ever calculate the value of one's CPP that way.  CPP is a DB pension plan, a crappy one, but DB nonetheless.