I haven't been on the receiving end of an attack, but I've sent some out and so far they are 4 for 4.
I sent the $5000 team out three times and a $2000 team once. Unlike the old Merryweather kill squads or the Mugger they seem to come prepared and won't give up until they are dead. I was able to get good camera angles on one of the attacks and the team showed up in an armored Schafter. In another attack, the target player suicided, and while that got the police attention off his trail the team followed him around for over 5 minutes before getting the kill.
Not sure if you get a refund on a failure (team was killed or target left the lobby).
While not as flashy as the Orbital Canon, the Facility Security Room is $125,000 less to add and a mere 1%, or less, of the cost for each kill. Plus you get another Weapons Locker and free guns (ammo) and sticky bombs every time you enter your Facility.
You can observe the strike with cinematic views, but you have to use the pause menu map to see where potential targets are before ordering the strike. No observing the lobby, like the Orbital Canon has.