Outside, the emergency rescue team of the Civil Defence Force (CDF) scoured through the rubble. With little training and limited equipment from Britain, America and elsewhere, theirs is a task as grim as it is dangerous. When there is an attack on residential areas, they race in to search for survivors and - as often as not - to recover bodies. In the last year, eight crew members have been killed as they brave bombs and bullets to rescue others.
What does "as often as not" mean here?
I also would appreciate your help, determining what the word "theirs" refers to.