I think it might be a bit of a "gray area", but I also think that most tax professional say "no", it is not deductible.

Once of the requirements it that the mortgage much be secured by "such" residence.  Although some people might interpret "such" to refer to any "qualified residence", I think most people read it as referring the THAT residence.

https://www.law.cornell.edu/uscode/text/26/163#h_3