Can the investor still trade their shares when a voting trust takes over?

As the text says, the shareholders are given a voting trust certificate which gives the shareholders the same rights as the original shares held with the exception of voting privileges. This means that they are tradeable on the markets. Only if the shares are cancelled or halted or if the company fails its listing requirements are they not tradeable.

So, provided the company meets its listing requirements it will remain on the exchange it is listed with. Once it fails to meet its listing requirements, it is then removed. As a shareholder, you would be paying attention to the fortunes of the company. And so you may decide that holding such shares may not be in your best interests. Thus your exit option - sell the shares.