I'm sure of what you mean by share info with each other, so I assumed a related portat.
I created two new files with one table each, related the two files/tables and then created a portal on A that showed records from B and allowed creation of new records in B. It worked on the iPhone exactly like it did on a mac.
How have you set the file path from the two files, I used relative file path as it is the simplest and since the iPhone doesn't have directories may be the only one that works the path I used was simply file:fileName.
Many thanks Bumper, working fine now, seems that was the issue.