I think one thing people aren't considering is that observations seem only to have been made west of Laird. Are there any observations at Mount Dennis? Hasn't there been talk of operationally short-turning some (peak?) trains at Laird.
I don't see how speed or dwell times would impact frequency. If they are all moving at the same speed, with the same dwell time, then they could move at 1-km an hour with a 5-hour dwell and still run every 3 minutes. It's all very silly of course ... but it doesn't impact frequency.
Traffic lights might be interesting - but what's the maximum traffic light cycle? I'd think you could easily run double that amount without much issue. And simply hold the occasional car at a stop, if the car ahead is too close, so it respaces. But that will be a potential issue, for the short distance where there are multiple lights.