There is no tax until we keep using bitcoin as bitcoin but still it is not possible yet so we need to convert our bitcoin into fiat so bank is essential so our earning will be recorded so we must need to pay taxes according to our income.
There's no need for the bank to get involved with our bitcoin income. Paying tax is essential whether bitcoin isn't recognized then the only thing that we must do for declaring our tax is to volunteer ourselves going to the tax bureau and declare your bitcoin income.
They can track using the bank details, because banks may be asked to provide details if account is being open for btc transactions or any suspicious transactions happening regularly than those details will be forwarded to them and then you will be under scanner.
They can and they can't. If you use an exchange that is sending payment through banks then for sure you are obliged to pay the tax because it is recorded to the bank's system and audit.
How come the governement of my country in asia where I lived will scrutinize that part, since there were many type of money trasfers now offered in different countries right now. Definitely the private sectors whom doing the business of money transfers were really required to pay their taxes, but in our side as a trader of the local exchange site we already paid charges while doing the transactions with them. My advice for this matter, please avoid sending huge amounts to bank directly, just do the transactions separately or the other types of money transfers can do.