The US Marshals are not the only federal law enforcement agency doing something like this. According to documents I obtained through a FOIA in 2012, ICE has purchased an airbourne mounting kit and paid for airbourne training for their Stingray II cell phone tracking gear.
See: https://www.documentcloud.org/documents/479397-#document/p44
yep. The cell phone tracking has actively been used for tracking and targeting in Ukraine/Russia war on Donbass by both sides.