Start dedicated server
log in
on the CLIENT execute

playerServer = player;
publicVariable "playerServer";
"test" addPublicVariableEventHandler {hint str (_this select 1)};

create helicopter on ther SERVER

heli = "B_Heli_Transport_01_camo_F" createvehicle position playerServer;

Get in cargo for example then execute on the SERVER

test = assignedVehicleRole playerServer;
publicVariable "test";

hint shows []

now execute the same on the CLIENT

hint str assignedVehicleRole player;

hint shows ["Cargo"]

Now get out of the heli and change helicopter locality to client, execute on the SERVER

heli setOwner owner playerServer;

Get in Cargo seat again and execute on the SERVER

test = assignedVehicleRole playerServer;
publicVariable "test";

hint now shows ["Cargo"] and it works for any seat