Questions about a fire suppression system breaking
Wet fire sprinkler systems are installed where the spaces are heated. Dry fire sprinkler systems are installed where there is no heat, (i.e.: attics, parking garages, etc.)

If your sprinkler system failed “where it passes between condos” then I suspect each condo wall is insulated but not between them. (Code requires a “fire separation” between units and a “sound wall” between units.) This is easily accomplished by building two separate walls. The space between them is generally not heated. 

So, the “wet” system that passes from unit to unit is probably going to freeze...the water in the pipes is stagnant (not moving) so easily frozen. 

This is a “design error” not a “repair issue” from 5 years ago. Your system needs to be re-designed to account for this error. 

The statue of limitations is 10 years in the U.S. for designers. If it’s been less than that I’d contact the architect/engineer that designed the building and sprinkler system. If it’s been longer, I’d notify the HOA they have a problem that will continue...mold is a byproduct that must be corrected. (BTW, if your insurance company finds out mold is an existing condition, they may not cover you...be careful what you tell them. I hate insurance companies...I’ve spent a lifetime arguing with them.)

BTW, “dry” systems have an air compressor that keeps air in the sprinkler lines 24/7. When a sprinkler head detects a fire or an alarm is pulled, the compressor is shut down which allows water to flow through the lines and out the heads. (Do you have a compressor? Was it shut off? The electrical breaker for the compressor should have a lock on it.)

You say there was a 3’ split from 5 years ago just discovered. If so, how could the dry system work? 

If your condo burns down, your insurance company could deny the claim if the HOA or maintenance did something to disarm the sprinkler system. 

I’d get a consultant to review your system, including taking mold samples. (If I lived there and my son didn’t graduate from Harvard, I’d blame mold and sue the HOA. I’d probably have a case too.)