Can research experience in one subject area be relevant to applying to a master's in a different subject area?
Of course the best scenario would be that you can prove you are capable of independent or supervised research activity in the field of interest of those organizing the master.

However, in my perspective field competence is not the only important element, as methodological competence and evidence of successful research endeavors is also crucial.

Personally, as a mentor of dozen of trainees at different levels in medicine, cardiology, and biostatistics, I like most those people who can do stuff independently or with limited supervision, somewhat irrespective of the topic of interest. 

So, if you can prove you can achieve in research (or any other similarly challenging field) with limited supervision, then even if you are applying for something off topic with your prior experience, you're still a potentially appealing candidate.