Well, only one episode that you know of. Which says nothing of material that may have been shot in secret during that period that you know nothing about. It's not like there are other project compromising Moffat's (or Gatiss') availability to do that. After all, "Sherlock' is on prolonged hiatus due to "NuTrek 2" and "The Hobbit".
wrapped in July. The second phase of The Hobbit
filming wrapped in September. (The first phase was pre-Sherlock
II filming. The third phase, the reshoots to fashion the third film, commence in May.) Sherlock
was to film in January (at which point Freeman would have been finished with Hobbit
Filming has been pushed to March (which is the latest it can film to fit before Freeman is due back in New Zealand). Last month Cumberbatch was filming a Julian Assange biopic; he either took that role because Sherlock
's filming dates had moved or Sherlock
's filming dates were moved because he took that role. Personally, I think the former possibility is more likely; Cumberbatch doesn't strike me as a diva who would throw an entire production off by two months because he took other work, plus we know that as of the beginning of the month the Gatiss and Moffat scripts for Sherlock
In short, the oft-cited reason for Sherlock
's filming delay -- Star Trek
and The Hobbit
-- has no basis in reality.