.... -0-
ok, let's put it this way: GB is nothing more than a module in the generative grammar, to be put on a par with such other modules of the theory as X', Case theory or the Theta Theory, although it has been quite incorrectly treated as though it were the whole of the Grammar (Chomsky, 1995b, p.30).
The sentence I believe can be interpreted this way:
1. There is an x such that x is subject to the action of 'training' such that x is intended to carry out the action of 'killing'.
Where X = the agents
According to the generative grammar, this clause involves, as usual, quite complicated and interwoven elements in action: 1. ECM 2. Move A (Alpha...) 3. Passive morphology (EST)
(i) The agents are (for the sake of simplicity, I omit the irrelevant Past tense here) trained to kill
can be interpreted as having the underlying structure of:
(ii) e train [Passive+, Present, Agr pl+] TP[DP SPEC [the agents] T'[T[to] VP[V[kill]]]]
As passive morphology makes the Verb assign no theta role to the Subject, such a sentence as:
* The Agency are trained the agents to kill.
is ungrammatical. However, on the other hand, as the Projection Principle mandates that every Agr P must have a Subject, a construction like:
* e are trained the agents to kill.
is impossible as well. Therefore, Experiencer NP 'the agents' moves to fill the Subject role (note that expletives are used as a last resort ---> in its ordinary sense, bringing no syntactic import: if there is any candidate eligible for filling the Subject A position, then that candidate will be used instead of expletives, such that *there / it are trained the agents to kill is ungrammatical)
There's still the TP left to discussion: as there's no Agr present, the TP does not assign Case to its SPEC. It is the Verb 'train', which governs the TP, that assigns Accusative to that DP. (as governor governs SPEC of the branch as well)