Joey, Trevor, Ann, Carol,
"However, condo unit owners should not have to bear all of the costs if retrofitting is the most practical solution."
Why shouldn't they?   
Just require signs in front of every condo, like you do for restaurants.  
Green "Sprinkler System" or Red "No Sprinkler System" 
You may also allow building inspectors to assign a Yellow sign for buildings that have an acceptable substitute, such as conversion of dry standpipes to wet standpipes with hoses that can be used quickly by residents and firefighters)
(and a fine for hiding the sign)
And don't you think that Condo Associations of buildings without sprinklers should immediately require an emergency increase in assessments to pay for improvements?  Where is that bill?