Just wanted to update with my transit experience for posterity. I arrived on EK and needed to get boarding passes for my onward SQ flight. The transfer desk could not help but the on-arrival visa desk placed a transit visa on my passport so I could enter Sri Lanka and go back through ticketing. You need a lot of time to do this - there are multiple checks to exit the airport and to get back in. Thankfully I did have plenty of time (too much.. had to wait for the SQ ticket counter to open).