And from what I understand it's worse now because the soft drink syrup mix and the CO2 are no longer in the same tank like they used to be. Newer systems have the syrup in cardboard surrounded plastic bladders with the CO2 fed in by one main large tank to the individual dispensers.

If there was a leak in the older premixed tanks, while it was still a danger, today's systems present an entirely different problem. Most modern systems have several feet of CO2 lines that are fed by one large CO2 tank. If the tank, regulator, or any of the lines leak or malfunction within the system, a far greater amount of CO2 will be released a lot quicker and can saturate smaller enclosed rooms like stock rooms, utility rooms, basements, etc. Most systems are required to have Leak Detection alarms but I don't believe that is always the case in certain situations and regions and if it's like anything else the testing and maintenance of these systems probably don't rank high on somebody's to-do list

And this hazard is possible in just about every gas station, restaurant, etc. that has carbonated soft drink dispensers. A quick search will tell you that it's not really all that uncommon with the concentrated tank systems that they now use.