@Boney, two questions.
(1) can Mathilde combine Shadowsteed and Night Prowler to ride rapid circuits of the city without being noticed?
If so, then if Talabheim (pop 72,000) is about the size of 1550 London, about a square mile, I'd imagine she could patrol the city fairly intensively as long as her attention held out.
This would be a point in favor of "with the Longshanks": she could hope for a good shot at personally spotting Alberich, even if he hypnotizes whatever Longshanks he encounters.
(2) are the tunnel entrances a narrow enough patrol circuit that "with the Tunnel Brigade" Mathilde could expect to detect Alberich's presence approaching? Or is the Tunnel Brigade choice just a way for her to get to the fight faster, still trusting someone else to spot him?
Of course, "with the Tunnel Brigade" is a bet on Alberich leaving by the tunnels. But I can't tell whether the bet is a "Here I can detect him myself, even if he hypnotizes the regulars," or if the bet is just "Here I can join the fight faster, as long as someone does spot him without getting hypnotized."