The OSP Airplane works with many agencies statewide. If those agencies also use MARCS, then that's how they'll communicate. If they don't, then 'Intercity' and 'LEERN' become the first two logical options. And if an agency doesn't have access to either, the plane can still access any countywide frequency that it needs to.
Up here in the Snow Belt, I've heard the OSP Airplane a few times over the summer...When they're working with the Chardon or Ashtabula OSP Posts, they can be heard on the post's Tac Channel on MARCS...I've also heard them on 'Intercity' 155.37 a few times. They used it when they were working with Euclid PD, clocking speeders on I-90. I've also heard them use Intercity once here at home. I could only hear the plane (no ground units), but it sounded like they were somewhere in Trumbull County. I have personally never heard the OSP Plane on LEERN 154.935 from up here.
And as for LEERN in this area, the Ashtabula LEERN Talkgroup on MARCS is currently patched to 154.935...In Western Lake County, Police still use LEERN to try to talk to Euclid PD during high speed pursuits that lead them West on I-90/Route 2. It actually happens somewhat regularly (apparently, when a crackhead steals a car in Lake County and gets pulled over, his first instinct is to run back to the hood)...I also hear LEERN used in Cuyahoga County's Hillcrest/East Suburban region, but 90% of the time it's just someone keying up the mic and playing song clips (somewhat amusing, but also pointless). I don't think I've ever heard anything on LEERN in Eastern Lake or Geauga Counties in the last few years.
Eventually, 154.935 will likely be phased out and LEERN will be exclusively on MARCS...But hopefully the OSP isn't getting ahead of themselves. That time hasn't come yet. There are still MANY rural areas in Ohio that use VHF-hi for Law Enforcement. In those areas, 154.935 and 155.37 should definitely still be monitored.
