In regards to the maxi-cosi car seat, I use mine just fine. It is the cabrio and quickly snaps onto my quinny stroller so it takes about a minute from curb to taxi. I use the middle seat in the taxi and quickly secure the seat belt up and over the car seat. It is designed to do this and so far the car seat has fit in every taxi. As far as the excuse that the taxi drivers won't wait...tell them too, who exactly is paying the fare anyway! And I have yet to encounter a taxi driver who won't wait for you, most are parents themselves. My maxi-cosi even fits in the minibuses too!
I'm Canadian and it drives me crazy how many parents do not restrain their children safely in vehicles here. THE LAWS OF PHYSICS ARE UNIVERSAL!!!! If you don't put your child in a car seat in a moving vehicle and that moving vehicle is in an accident, your child will get hurt! If giving yourself piece of mind means that you have to take the time to put them in a car seat, why wouldn't you? Your child is worth the added fuss don't you think?