Workers in the abattoir are followers of a number of religions

We understand that the meat slaughtered by the people of the Book (i.e. Christians and Jews) is permissible to Muslims. This cannot be argued since it is found clearly in the Book of Allaah. Of course we realize also that there are a few differences of opinion amongst the scholars in certain circumstances. Today I wish to ask about a particular circumstance: We live in a city in Canada and as you may be aware, Canada is a country made up of immigrants from all parts of the world. Therefore, if you were to go to a slaughter house you would find people from many different backgrounds working there. You may find Muslims, Jews, Budhists, Christians, Sikhs, atheists, etc.. working there. Of them there are those who are responsible for killing the animals. Generally it is not known to the masses who it is that is killing the animals (i.e. it could be an individual of any faith, we have no guarantee who it is) and so can we say that since we live in such a country then it is not important to know that information and that we should just eat the meat found in the market place? I ask this keeping in mind that there are Muslims who do slaughter in the Islaamic way and sell that meat. In fact dear Shaykh, this is a fitnah for many people and the problem is that they ask the Mashaayikh in most cases without explaining the details I just mentioned. It would be most helpful if you could clarify for us this issue in some detail.