If you require hourly/non-salaried employees to attend concalls and check ticketing systems during off-hours, expect to pay OT for that time. Smart hourly employees will find the broadest interpretation of your requirements to rack up maximal OT comp for minimal work. Serves you right.
If you employee non-hourly ("exempt") workers, there is nothing here for you to be concerned about. That's why they call it "exempt".
I certainly sympathize with employees who are normally horuly and called up extensively outside of hours, however they certainly have an obligation on their part not to check their e-mail or do other work related activities when they are not on the clock and most companies require hourly employees to receive approval before working overtime hours.
For salaried employees, this seems a nonissue in most cases. Unless they are specifically told otherwise, they can normally expect to work more than 40 hours, and they are also normally in either management or creative roles both of which can face deadlines requiring far more than 40 hours to finish the necessary work.
Heinlein suggested in his last novel (To Sail Beyond the Sunset) that telephones in the home killed house-calls by doctors, it became too easy to contact the doctor for any little thing that was bothering you. So it would not be surprising to find even easier and "more connected" versions of the phone having similar effects.
When I was an hourly contractor, and was on call I would charge for calls I received outside of work (rounded to the nearest hour, so if the call took 5 minutes I would charge for the full hour) my boss approved all those hours. Of course answering an email that is not urgent is something I would wait until the next day to do. Also I will admit that if i was taking a call it was typically nothing mundane usually something was blowing up.
If you require hourly/non-salaried employees to attend concalls and check ticketing systems during off-hours, expect to pay OT for that time. Smart hourly employees will find the broadest interpretation of your requirements to rack up maximal OT comp for minimal work. Serves you right.
If you employee non-hourly ("exempt") workers, there is nothing here for you to be concerned about. That's why they call it "exempt".