As far as I can tell, he is being politely ignored. There is another fellow from Canada, the University of Toronto, who has been saying substantially the same thing. Here is a recent reference.
Modified Gravitational Theory as an Alternative to Dark Energy and Dark Matter
Authors: J. W. Moffat
Comments: 17 pages, no figures, LaTex file
The problem of explaining the acceleration of the expansion of the universe and the observational and theoretical difficulties associated with dark matter and dark energy are discussed. The possibility that Einstein gravity does not correctly describe the large-scale structure of the universe is considered and an alternative gravity theory is proposed as a possible resolution to the problems.
Full-text: PostScript, PDF, or Other formats
I referred to both Cahill and later to Moffat's work on the physics forum.
The response to Cahill paper was remarks like, "It's getting difficult to tell if someone is or is not a quack"
The response to the Moffat paper was, "He has been saying that for years. It's nothing new"
So even though there is hard evidence supporting Cahill in the lack of dark matter in spherically symmetric galaxies and in bore hole data, the physics community seems unwilling to give up dark matter and admit that general relativity is a special case of spherical symmetry. The gravity measuring satellite, which almost got cancelled by Bush's new space program, may shed some light