Not many female groups as far as i know, exactly coz not many are classically trained.
also it is diff to pin up the music of Il Divo exactly - after all they do sing Pop songs which so many Pop artists do,,,but what makes is different is how they sing it..
We have 3 Graces which has a Pop, Classical and R&B singer.
You also have Celtic Woman - not sure if they are still around - but some of their songs overlap
Also Il Divo's supposins success has spawned a whole lot of Cross over artists who may wanna try and see if u like - Sarah Brightman, Kelly levesque (Duo voci), Camilla Kerslake, Charlotte Church, kAtherine Jenkins, Vanessa Mae, Hayley Westenra, .. just google for cross over artists... there are more i dont know of..
There are other male bands out there too...Canadian tenors, Adoro, Celtic thunder.. but i dont find them exactly the same...but you can try em out too
Of course the great Bocelli figures... russell watson, Josh Groban too
Hope this helps