So say I have a unmodified phantom, and a Lambda opperated by Colonel Jendon, and he passes his target lock on to the phantom. Can the phantom spend it during combat provided he is within range and has the target in sight? He lacks the target lock action, but he now has target lock....

Yes. The action allows you to gain a lock, but (as you note with Jendon) it isn't the only way to acquire the lock, and if you have the tokens you can spend them regardless of how they got there.

Thank you, I was not sure that was how it worked, so better ask then build a list that does not work as intended.