That's a job for THE MIDDLE MANAGER!! (imagine a crappy super hero)
No, seriously, do not step over your boss to talk to theirs. That's like, the job your boss has, and they might get pissed at you, and, depending on pettiness level, make your life worse. Talk to your boss, explain how and why that's a problem. Make it clear you expect them to solve it.
If and only if they say they can't do anything, you may consider talking to your boss' boss. But not the other team's boss. Before doing that, I'd have hard financial evidence, like the other commenter suggested. Log your hours in their time buckets for at least a month, get others to join you in doing the same, get a report with total amount spent. Then you turn again to your boss and maybe include boss².
Nothingeverhappens moment.