The regression only remains active during Feral Frenzy, after that it ends. During Frenzy, that addon shows you the generator progress through the gen auras themselves and then outside of Frenzy the regression isn't active so you won't see the white aura from Surveillance since they won't be regressing anymore.

You can, however, stack it with other regression effects such as a normal generator kick or Ruin regression to achieve increased regression during Frenzy (this would be like having the pre-nerf Ruin for example), and then it will still be regressing outside of Frenzy too just without any bonus from the addon.