Agapanthus are almost un-killable. Do you know what type you have? Some are deciduous and some are evergreen. Whatever form though, I would not expect them to have been making much growth over winter.
So, yes, theoretically if there has been no damage underground to the plants, they should grow back vigorously in warmer months.
One word of caution, if you have a small garden bed you may need to re-think because Aggies can have a very substantial root system which makes it almost impossible for anything else to grow close by them, and also makes them a job and a half when its time to divide them.