Depends on how it was installed.
If it was installed on the Main line ( Constantly charged line) and the system has a Master Valve that prevents the Main line from being constantly on then it is fairly doable to turn it on with out the sprinklers running.
If it was installed into the lateral of a particular zone, the hose bib will only work when that zone runs. ( For example, You have to turn on zone 2 in order to run the hose bib) Then that's just how that is, you could re-work it though and put it on mainline
Open up your controller and look for a port that's called MV ( Master Valve) / PUMP , look and see if there is a wire in there and let us know.