Sentence ((43)) is ruled out by the <assign-comp>= inf nil/ind nil/ecm feature on the subject extraction tree for ask, since the <assign-comp>=for feature from the for tree will fail to unify. However, ((44)) will be allowed since <assign-comp>=ecm feature on the expect tree will unify with the foot of the ECM verb tree. The use of features allows the ECM and for-to constructions to act the same for exceptional case assignment, while also being distinguished for that-trace violations. Verbs that take bare infinitives, as in ((45)), are also treated as ECM verbs, the only difference being that their foot feature has <mode>=base instead of <mode>=inf. Since the complement does not have to, there is no question of using the to tree for allowing accusative case to be assigned. Instead, verbs with <mode>=base allow either accusative or nominative case to be assigned to the subject, and the foot of the ECM bare infinitive tree forces it to be accusative by its <assign-case>=acc value at its foot node unifies with the <assign-case>=nom/acc value of the bare infinitive clause.
The trees in the TXnx0Vs1 family are generally parallel to those in the Tnx0Vs1 family, except for the <assign-case> and <assign-comp> values on the foot nodes. However, the TXnx0Vs1 family also includes a tree for the passive, which of course is not included in the Tnx0Vs1 family. Unlike all the other trees in the TXnx0Vs1 family, the passive tree is not rooted in S, and is instead a VP auxiliary tree. Since the subject of the infinitive is not thematically selected by the ECM verb, it is not part of the ECM verb's tree, and so it cannot be part of the passive tree. Therefore, the passive acts as a raising verb (see section 9.3). For example, to derive ((47)), the tree in Figure 8.7 would adjoin into a derivation for Bob to talk at the VP node (and the <mode>=passive feature, not shown, forces the auxiliary to adjoin in, as for other passives, as described in chapter 12).
Under the TAG ECM analysis, this fact is easy to implement. The foot node of the ECM passive tree is simply set to have <mode>=inf, which prevents the derivation of ((50)). Therefore, for all the other trees in the family, to foot nodes are set to have <mode>=base or <mode>=inf depending on whether it is a bare infinitive or not. These foot nodes are all S nodes. The VP foot node of the passive tree, however, has <mode>=inf regardless.