Plausible deniability only works if any doubts are actually interpreted in your favor (which, as history shows, isn't guaranteed in practice even in legal systems where it should be in theory), and it's easily possible to make laws that turn most practical options into crimes.

Yes, it's plausible that the non-approved software stack on your phone isn't doing any illegal encryption, but that fails if having non-approved OS on your phone a crime by itself.

Yes, it's plausible that the TrueCrypt volume you have doesn't contain anything bad, but that fails if mere possession of TrueCrypt tools is a crime by itself.

Yes, it's plausible that the encrypted traffic sent to/from your phone didn't contain anything bad, but that fails if having any encrypted traffic not going through state-approved MITM https is a crime by itself.

Etc ad infinitum. Don't underestimate the coercive power of gov't if they actually want to restrict something. Technical means can protect you only if you physically live outside of their reach.