A-ha, I guess you are developing an MT adapter.
However and unfortunately, if you are working inside that tranlsate() method of the WSMTAdapter class, I think there is no way to get the contents of the placeholders.
But one of the ideas is to wrap the WSMTService class.
This class comes with the following method.
public void translate(WSAssetTranslation wsAssetTranslation, double v)
You might need to implement all of the methods provided by the WSMTService class, but by overriding the above method, you can get the WSAssetTranslation instead of just a simple string.
Once you can get the WSAssetTranslation object, you can get the placeholder contents as shown in my last reply.
Sorry, it is totally figuring out inside my head without any actual testing. This is little annoying of implementation, but I think feasible.
If I can find availability myself, I will try this. Otherwise, testing by yourself might be faster:)
A few notices.
This way of MT implementation requires users of your MT adapter class to use your wrapper class of the WSMTService instead of calling the WSMTAdapter directly.
Please do a good enough testing since you will implement all of the methods in the WSMTService by yourself, to make sure there is no side effect.