I'm guessing ride bikes to the bridge and leave cell phones at home? That's the only thing I can figure. They had to carry quite a bit of gear.
The Brooklyn Bridge has a few features that make it comparatively easy to pull off. Here's a street view link that should give you an idea: https://www.google.com/maps/@40.705226,-73.995817,3a,90y,130... - The bike+pedestrian path is suspended over the roadway. - There are some suspension cables leading from the suspended pedestrian path, and trusses leading to the other cables. - The cables are pretty thick and have…
Even with permits and DOT assistance, the SWAT team came out after them and halted traffic on the bridge.