In my mind, the school bus always went straight to LA where the slayers recuperated before heading off to Europe. According to the onscreen timeline, that was 18 days before Spike reappeared. I always imagined that was at the Hyperion, just before Angel moved in to Wolfram & Hart and that they got on their way quickly, within a few days.
I think they knew Angel was working for Wolfram and Hart, hence the "where do you think my orders came from" line from Andrew in Damage. I always took that to mean Buffy. I don't think she knew Spike was alive. If she did, I think she would have tried to see him. Perhaps everyone (Buffy, Giles, etc.) found out after Andrew went to LA because he seemed pretty surprised, too. By then, she would have been pretty involved in building her base in Scotland.
I doubt she and Angel ever talked on the phone. I think it would have been too painful for her. She probably let Giles, Willow, and the like keep up communications from a business perspective. I guess we'll find out a lot more at the end of S8.
