This is from Wikipedia, so ...
"If a player is on the 40-man roster but not on the active major league roster, he is said to be on optional assignment—his organization may freely move him between the major league club and the minor league club. The rules for this are as follows. (In all cases, an assignment of a player on a major-league disabled list to the minors while on a rehabilitation assignment does not count as time spent in the minors.)
Once a player has been placed on a team's 40-man roster, a team has 3 option years on that player.
A player is considered to have used one of those three option years when he spends at least 20 days in the minors in any of those 3 seasons."
So it appears the option year have nothing to do with the active (25 man) roster and everything to do wth the 40 man. Once Vazquez was put on the 40 man roster prior to the 2013 season, the options kicked in. He didn't have to be called up to the active roster; being on the 40 man was enough.
This is backed up by the words used in the SoxProspects tranasactions: the March 2013 and 2014 (and this year's) verbiage is "optioned", not "reassigned" or other designation.