They do have a way to communicate with local LE and vice versa.I understand having things they can't/don't share with local LE, but if the SS is relying on local LE to help and if they have delegated significant security tasks to them, then it's negligent to not have a way for them to communicate with one another. I'm not saying they have to share secret routes or info that only SS needs to know, but how the heck are they going to learn of a threat if local LE are in charge of watching for these threats and then they can't in turn communicate that to the SS?
It works all the time, during hundreds, if not thousands of events every year, for decades.