I've had two different experiences with this. Routinely, if I am flying ex-Europe with my US-sized carry-on, and the agent makes a fuss over it and I have to check it, I will take it off the belt while clearing C&I in the states, and rip up the tag. I've never had a problem with it.
Also, recently flew PHL-BRU, but had a problem with my ticket. Though I got to the gate an hour before departure to talk with a gate agent, I was only able to board just as the other GA announced that all larger carry-ons will be checked to the final destination. The GA I was talking to offered to blue tag my bag, until the other GA said that they aren't allowed to blue tag internationally (I'm assuming all TATL/Brazil, excluding Canada/Central America). I then asked if I could just try to find an overhead bin, because the flight wasn't 100% full, and I should probably be able to move stuff around to find a space on the 757. The other GA said "Go for it, but I better not see you come back up here". There was room for at least 5-7 rollaboards when I got onboard, so it ended up being a non-issue.