Agreed that this is remedial, similar to the situation with CBC Radio 1 in Vancouver where their original 690AM coverage had nasty issues in a variety of Lower Mainland spots so 88.1FM was also assigned. Ironically they later had to also activate on 88.5FM for areas further up the Fraser Valley. I can't remember the last time I used 690AM to listen to them while in the Lower Mainland. Combined with CBC Radio 1 and Radio 2 propagating from over in Victoria the CBC's two networks are well represented on the FM dial.
The Golden Horseshoe has such a crowded FM dial that it is a bit of a feat for IC to have found a frequency that gives the new service a coverage bubble in downtown Toronto.