I have changed white collar jobs (not a teaching job) and each time a Release Letter from the former employer was required. However, I am also unaware of any strict legal requirement in this regard. In retrospect, it seems to be just another way to keep foreigners out of the job market and/or labor pool.
I agree with Richard, its is unlikely that there is any coordination between various agencies, especially between local (as opposed to central gov’t) agencies in different jurisdictions.
However, given that the position is English teaching, the most relevant agencies are clearly the local Departments of Education at the City/County level. To my knowledge, the Ministry of Education doesn’t get involved in the issuance of work permits except for those teaching in national universities/colleges.
Regardless of whether a Release Letter is a legal requirement under relevant laws/regulations, or is a requirement that a particular case examiner “feels” is necessary to impose even though there is no legal basis (and as we know, such can often be the case with bureaucrats in Taiwan), an important message here should be the importance of leaving on good terms.
That is to say, if bad blood develops, the former employer could make life difficult with a couple of phone calls and accusations to the Ministry of Education, the Foreign Affairs Police, etc. Unfortunately, we have heard such stories before.
Of course, if the foreign community wants to challenge this “Release Letter” requirement, someone needs to step forward and file the relevant lawsuit. Maybe Richard can provide some additional assistance in that regard.