In this question both answerers suggest that papers in special issues are likely to receive more attention and citations than those in "normal" issues. Wiley have also made the same claim. Can anyone provide a source that gives data supporting or refuting the claim?
It might be pertinent to consider that the journal editors will undoubtedly commission their special issues in subjects that they consider to be 'hot topics', with the aim of boosting overall citations and of establishing their journals in those areas. So there's an element of selection going on even before you consider whether a community might respond more favourably to a paper just because it's in a special issue.
No source, sorry.
In general, there should not be any dependency. In some areas, the only citations you get are from people you personally introduce your own work to. The venue where the paper is published is of second relevance. In my experience, for example, my most cited paper is a technical report, although I do have journal papers, even published in special issues.
What might potentially play a role in citation counts is whether special issues enjoy free access or paid access.