As far as I know, to view solutions and test data to problems in the Gym, you need to be able to enable coach mode (the requirements are being Div.1 and having some number of contests).

However if you clone the contest to a mashup then any submission made (and all tests that ran on that submission) in the mashup can be viewed by the contest manager (which defaults to the user). It doesn't seem to work for viewing the submissions of others that haven't participated in the mashup so it's not exactly like coach mode but it's better than nothing I guess.