The point of Greyball is that it was an attempt to get away with operating without a license in Portland (and some other US cities), by making it hard/impossible for agents of the regulator to get rides on the service to gather evidence. And despite getting caught Uber are still able to operate in Portland (I wonder how much that cost and who received what...)
Uber (London) has only ever operated under a valid license, so Greyball isn't really relevant as Uber would have had no reason to deploy it in London - they weren't hiding from anything.
(Uber could, theoretically, have drivers that didn't have a private hire license, but that would be suicide for the London operation. So I suppose TfL might want to have its own employees be able to take random journeys to gather their own evidence of whether drivers are legit or not, but that's much different from knowingly operating without a license. Also the tactics used to identify the transportation agencies employees in Portland, in order to greyball them, wouldn't work anywhere near as well in London:
https://en.wikipedia.org/wiki/Greyball and now that Greyball is known it should be quite obvious to anyone that has used Uber whether they have been Greyballed or not.)
Also, from that article, the point of Uber's separation between Uber BV (the Dutch app company) and Uber London Limited (the minicab firm that gets all of its jobs from Uber BV) is that it is Uber London Limited that requires the operating license from TfL, not Uber BV. ULL doesn't have Greyball itself as it isn't in charge of the app. TfL might find they have no legal right to deny ULL an operating license based solely on the actions of a separate legal entity (Uber BV) no matter how awful their practices are (or have been).