Varig hasn't had over-booked flights lately, unless they cancel one and they move all pax to their immediate next flight

Carefully expect upgrades IF you're Smiles Diamond on a nice day - They've been instructed to have pax deplete their mile accounts to relieve their mile burden. Positive spin is that you might get accepted a 25k upgrade award on a fare basis that would usually not be eligible for it at all.
Anyway, truth be told, RG has been cancelling flights in South America - but check-in (and Gate) positions are instructed to immediately have tranfer pax to other airlines and endorse tickets.
This week, twice, I was blown away when RG told me that their flight had been cancelled and whether I'd rather be protected on TAM or GOL within my expected window for departure.
I chose TAM - who by the way cancelled their flight as well and got transferred back to RG. No questions from RG, no hassle and politeness all the way.