First of all, newspapers often use present perfect and past perfect tenses in their articles. According to me, they use those because they give you some information/ tell a story, often to refresh your mind about certain facts.
To be honest, I can't come up with clear explanation.
I think that the present perfect makes this sentence and the fact that they have to let off 20.000 workers stronger. It has more impact because it is more related to the "now-moment".
But there might be another explanation as well.
What if you look at the sentence like this -> In the same week as GM took drastic action to stop the rot and Renault unveiled a revival plan Volkswagen (also) announced that it will lay off 20.000 workers over the next three years. This is a chronological order.
So, it might be possible that they used the present perfect here because Volkswagen was the last one of the three car makes which announced this news about giving workers the sack. In the sentence you have given us, they start with the news of Volkswagen. If you tell something which happened in the past in a non-chronological order you have to use the present perfect. It does make sense here. Although it happened in the same week.
Hope you understand what I'm saying here And I hope even more that I'm right
Looking forward to other people's opinion