I'm not sure if this is exactly what you are looking for but you can get a list of events the overlap a given cell in onBeforeCellRender using args.cell.events().
See also:
https://api.daypilot.org/daypilot-scheduler-onbeforecellrender/
And a related demo (this doesn't use args.cell.events() but args.cell.utilization() to calculate total cell utilization based on the events):
http://javascript.daypilot.org/demo/scheduler/resourceutilization.html
If need, you can also access the row data using args.cell.resource in onBeforeCellRender:
dp.onBeforeCellRender = function(args) {
var row = dp.rows.find(args.cell.resource);
var events = args.cell.events();
// ...
};