From their website:
Citadis is a class of low-floor trams developed by France based transportation company Alstom. It is built on a standard platform which can be easily customised.
The tram operates at an average speed of 70km/h and is capable of running on multiple electric power systems with or without overhead cables.
Unless you expect them to run at an average speed of 140kmph I think that the equiptment is not the problem.
As I said, they can run at those speeds, its technically possible, but its really pushing their design to an absolute limit. The amount of wear trains get under Metro style operations is significantly more than a tram style operations. Also don't forget that we're talking about Low Floor trains, where the bogeys and engines are fitted into a very tight physical space, meaning that they are even more prone to wear and tear (and for this reason, LFLRVs are often far more expensive to maintain than their high floor counterparts).
These trains COULD run at an average speed of 70km/h, but they weren't designed to run at that speed at 3 minute headways for 18 hours a day, 7 days a week. The "typical use case" for these trains would me mostly on street operation where its travelling maybe 20-30km/h, with occasional off street segments where it would reach that 70km/h - just like iON (and surprise surprise, one of these systems is constantly having mechanical and maintenance problems, while the other one isn't, I wonder why?).