An iodate - or a bromate for that matter - should easily be reduced to iodide or bromide by any available reducing agent.
Of course, photochemistry, developers in particular, are dependant on redox reactions and reducing agents. Having excess iodine or bromine in the halide emulsion will oxidise all the reducing agent you're using as your developer when you put the emulsion in the developer after exposure.
So, if you've got a little iodate in your iodide solution, or bromate, it might be workable - but you would have to increase the concentration of the developers / reducing agents, so there's enough to react.
Does that all sound plausible?
What do you all think?