The short answer is No. There is no an easy way to import a Portfolio expert back in EA Studio for now.
The long answer is - it is possible but requires some hacking. The Portfolio expert contains meta data for each strategy that is enough for the strategy recovery. There is same code at the bottom of each exported expert advisor.
You can copy the string of one of the strategies from you portfolio and to put it instead of the strategy code in an expert. Than you can import the expert back in EA Studio.
Sorry to say but you have to copy these wines one by one and to load the experts one by one.
A more hackers way is to see the format of an exported Collection and to make a script that will export the portfolio strategies in similar format. It must not be so difficult.