Well, Culture ARE the masters of reverse engineering. So, if any ship gets near their vicinity, then it's over.
And that's why competent Irkens use inter-galactic range transporters to steal their tech and study and start using it on their ships in another galaxy before invading. Now the Irkens are impossible to beat short of the Sublime in the Culture-verse.
Also, the Xeelee are way behind on inter-universal transport tech next to the Jjaro who can implant such a device in human size objects from what I continue to read about them.