While they have certainly taken the initiative here, I can’t see them holding this ground for long. But Russia’s offensive was already grinding along at a crawl, and seemingly losing steam. Forcing them to redeploy badly needed reserves from areas where they are already struggling might be the goal here. It might even provide some opportunities to push the front back at a few points. It is also a pretty big embarrassment to Putin, and can’t be good for morale among Russian troops and civilians.
Also, those troops arriving from the front will not have built up fighting positions and logistics, and will probably lack many of the tools deployed in Ukraine, like EW support. And they will be covered by UKR artillery and rockets. Maybe even JDAMS, SDBs and AASMs. UKR could also have moved an air defense battery to the border. At this point, we just don’t know what UKR has committed to this effort, and what the true goal is.
I believe the key to UKF success is ISR drones.
If ISR drones detect ruzzian efforts to "feed the fight" then all the items listed above can come into play.
I also believe FPV drones will play an important part in destroying ruzzian men & equipment long before they reach the battle.