Jim is quite right that Dave Paton is the best informed on the Australian
situation. You should watch for a paper in BioScience by him. I expect
it will be published soon. Graham Pyke and his co-workers have also
studied the problem in Australia and would be good resources to tap.
There is a paper by Camargo and co-workers from Brazil published in
Apidologie last year. That discusses the africanized bee and its impact.
Other Brazilian work is in preparation as well. I'm sorry that I don't
recall the actual reference. I can not remember if the recent reviews
in Bee World (a series of 3 articles by Sally Corbet, Ingrid Williams,
and Juliette Osborne) discuss the issue you raise. I am sure that they would
reply over BEE-L themselves if they could help.
 
To some extent the shoe has been on the other foot in S. Ontario, with
apiculturalists asking about the effect of non-honeybees on the honey
crop and the well being of honeybees. Some of us here have had some
interest in the importance of honeybees in the abundance and foraging
behaviour of other anthophiles, but I have not been able to find time
to follow up with any research.