Baluchistan has a long border with Afghanistan, and the border is looked after by levies and FC guys and not the army. And 1KM or 1mile is hardly any distance, especially in cars while on foot it would take 15-20 minutes. Many villages are even divided between the border, half on this side and half on the other side, even homes are situated right on the border line. Hundreds of passage ways are there, which can not all be looked. plus its not even sure if they came for the Taliban since its first of its kind, may be they were the private militia guys of some local warlord since Afghanistan is being run mostly by warlords and every warlords militia uses the govt uniforms and vehicles. Thus there are many questions yet to be asked and answered.
And as for the Taliban story, i wonder why can't the ANA catch something in their own country, that they had to come all the way here and try to find some. ANA/ANP knows well that if they do execute Taliban in such a fashion, the consequences for them would be very troubling as Taliban don't let go such things.
My guess is, this was something else, not a chase for Talibans, rather something personnel in nature. If ANA/ANP are so keen on capturing or killing Talibans, they have plenty of them on their side, rather many are right within ANA/ANP.