I've seen rules from both CT and T4 copy/pasted into MgT verbatim as rules. It's about 50/50 from each edition.
Since my question has nothing to do with T5, I moved this to a new topic in the Mongoose Traveller section ...
I am unfamiliar with T4 except in generalities (distinctive artwork style, variable dice task system, short lived parent company), but I do have the FFE CD for T4.
So rather than feed the 'yes it is - no it is not' ping-pong on the other topic, I wanted to ask:
Can you provide a specific example of T4 rules that were copy/pasted into MgT?