Well, as I said before, I reckon this needs to be split into two distinct camps: grabs and strikes.
Against grabs, someone is making contact with you, and you've got a fixed point of reference to work from. A good kenpoist should be able to turn a guy around and get a nasty arm lock on from loads of different grab positions (they're not hard moves), then either maintain the lock, break an elbow joint, or whatever. In these circumstances, then yes, I could see someone pulling off Gripping Talon, Crossing Talon, Lone Kimono, Conquering Shield, Obscure Wing etc. etc. etc.
Against strikes though, it's just not going to happen, but, this doesn't mean that learning the techs is a waste of time. Pretty much all of them (well, the ones that I know anyway) are against a single strike. We practice them by throwing the punch or kick, then standing there whilst someone finishes the technique off. People aren't going to do this.
Firstly, they're actually going to be aiming a you. I don't know what it's like in other people's schools, but no matter how often I tell people to actually get in range for a strike and aim at the target in our school, they don't. They throw punches that land anything from 10cm-30cm short of target, and often aim to the sides of people's heads for example.
Secondly, it's going to be full speed. Can you properly block sull speed and full power strikes? If you don't know, get someone to put some gloves on and properly try to knock you out, you'll soon find out.
Thirdly, they're not going to just throw one strike, they're going to try and batter the crap out of you as fast as they can. They're certainly not going to throw a single, step-through right and then just stand there.
All these things conspire against you, and that's why I don't think you've got a hope on hell of pulling off a full or even half a tech in a proper fight.
So, why isn't it a waste of time learning them then? Well, to my mind, you're learning lots of nice block/strike combinations, as well as lots of strike/strike/strike combinations. If someone takes a swing at you, you might be able to get a block/strike combo in before they throw another punch, then maybe you can get another block/strike combo in, that's still two strikes you've landed to their nil, if you can block them properly. Then maybe if you've got them feeling a bit dizzy with a couple of strikes, or winded, then you can lay in with a strike/strike/strike combination. So, you're still using what you've learnt. The point being that the strike combinations in kenpo are designed to be motion efficient, and to let you use checks and covers, so it's an advantage to fight with these combinations rather than just thowing your own left and right haymakers, like they probably are.
The important point is though, you need to turn yourself into a
dynamic fighting machine; someone who can use what they've learnt in a fluid and flowing fashion. The techniques as they stand are
static, and pre-prescribed. They don't adapt to the opponent. And in doing this, you also need to train yourself to think lightening fast, constantly working out where the next strike might be coming from, and where you can land your own strikes, as well as having good situational awareness.
Having said all that, people keep mentioning sparring and street fighting in the same context, and not making a whole lot of distinction (Jeff's got the right idea...). To me, sparring is a bit of fun you have with your friends in the dojo, no-one's trying to hurt anyone, and it's just a way to improve fitness and practice your blocking, nothing more. If you're training seriously, train for the street, not for the dojo, and make the distinction.
(All above is personal views.

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Ian.