I believe that a separate /48 per site is better regardless of whether or not the company has contracted with a single ISP for all sites, or not. As far as I am concerned if there is a separate access circuit, then it is a site and it deserves its own /48 assignment/allocation.
So aggregation is no longer a goal?
Aggregation is not harmed by the /48 per site decision. If an ISP wants to aggregate their IPv6 traffic, they will announce one block for their entire global network. Then, internally, they will assign /48s in LA from a western USA internal allocation and /48s in Hamburg from a northwestern Europe internal allocation. If those two sites happen to belong to the same customer, then they could assign the customer a /48 to cover both sites and carry longer prefixes internal so that LA traffic stays in or near LA, and Hamburg traffic stays in or near Germany. Of course, if both sites are different companies, or if both sites belong to the same company but they contract with different ISPs in each country, then the sites will get a /48 assignment without question. --Michael Dillon