Re their Tax exempt status.
This comes back, I think, to their vast quantities of cash, and their litigious nature. They were actually stripped of their tax-exempt status in the US back in I think it was late 60s? - They then slapped the IRS with a blizzard of law suits, and regularly filed, went to court, lost - for decades - until the IRS finally caved in, because of the drain on their resources that defending all these lawsuits represented. So Scientology paid what was effectively a token fine/back payment in taxes, and in return were re-instated as a tax exempt body.
It is also important to recognise that they have an extensive PR machine that lobbies ceasely for Scientology to be recognised as a religion in all of the countries they operate in. Some countries they have been successful, others less so. France is a hostile envirnoment for them - they have been classified as a cult, and were recently fined nearly a million dollars for fraudulent behaviour.
In the UK they are not exempt from tax, but are exempt from VAT - they are recognised as a not for profit organisation, rather than a religion.Despite that, it is recognised as a religion by the Prison Service and the Armed Forces.