Brittany Ferries have put out a statement confirming the arrangements using their existing fleet to provide additional sailings (their ships all accommodate freight). However I believe some of the sailings are Plymouth Roscoff which isn't going to be very attractive to hauliers using Dover Calais.
Anyway, it isn't about ferries really. The intention is to divert freight from Dover/Calais to reduce customs checks delays by using alternative ports. Same amount of freight but any additions on the Western Channel routes means that the Dover/Calais ships will be sailing correspondingly empty.
Plus of course any time savings hauliers might make at the alterntive ports are likely to be cancelled out by increased driving time on both sides of the Channel plus there is the extra fuel used by the lorries.
Usual ill thought out shambles unfortunately, just like plugging smart meters in homes that can't get a signal or cease to work if you change supplier. Total waste of money but there are boxes to be ticked so that's OK then!
It's only taxpayer's money after all.
Colin