Sure, the concept isn't too hard at all.
Basically, a few pets, namely the Ethereal Soul Trader and Alterac Brew Pup are interactable. The trader acts as any other vendor and the Pup gives you a drink when you interact with it. It is worth noting that once you receive the drink from the Brew Pup, it will seize to be interactable until the drink has been removed from your inventory one way or the other. The way we got around this issue was to have full bags so you could not receive the drink, and the pet would thus remain interactable.
So, since we know that Interact With Target sort of counts as a keybound click, we can use it in combination to having Click-To-Move enabled to send your characters walking towards any interactable target. If we do this with the pet, which should most commonly be right next to the character that has it pulled out, your other characters essentially be moving towards where that character is, creating the sudo-follow effect.
How you would choose to set it up is dependent on how your team functions, but often people would set the pet as focus and have a mapped key that would make their character target their focus (i.e. the pet) and use IWT. Alternatively I suppose a /target macro might work as well, which would leave your focus free to used for anything else you might need it for.
I will however point out that it is no outside the realm of possibility that the pet-follow will be nerfed in the WPVP phasings/areas, just like it was in Ashran and BGs later on, so it really it is not something you should count on being there as a given.