Actually, one would bar a cell for a certain reason.
In some cases; we have significant blocking on a cell. One way to reduce blocking is to bar the cell. In this way; it will carry only HO traffic.
On the other hand; sometimes a cell is barred because it has some firmware issue and it is understood every call it entertains will get dropped. In such scenario; we must bar the cell and also inhibit TCH assignment from Msc.
The MS will continue to listen the paging. But it can't respond to paging.
If I recall it right; if MS fails twice to respond to paging; it will trigger cell reelection.
Please correct me if I am wrong. My 2G has become rusty