No crossover, exactly.
The closest it came too was after Buffy defeated Glory and then died, in the last ep of the season for Angel, we see the gang return to find a very forlorn Willow sitting on the couch in the main hall of the hotel.
And you have too remember that the monks had either changed the memories of the entire world or just those that knew Buffy’s family, so even Angel and Cordelia would have those memories, so Angel probably knew about Dawn before Willow turned up.
ADM