Do game companies use third party game UI library or develop their own?

Is it possible to design a high quality game ui like in WOW by using UI libaries such as CEGUI and guichan

Almost universally each engine provides its own GUI libraries so no game companies don't use 3rd part UI libraries.

But is it possible to make high quality one using 3rd party libraries?

Almost universally each engine provides its own GUI libraries so no game companies don't use 3rd part UI libraries.

Extremely untrue, a lot of companies use scaleform or their own flash interpreter for their UI. There are also a few other 3rd party frontend options out there.

But is it possible to make high quality one using 3rd party libraries?

What do you mean? Can you make a UI that looks and feels like the UI in WoW using an existing third party library? Yes you can.