Hello, can i use e.g cross-training on Wing-guards in my Imperial list (with Temporary Alliance) ??

Some skirmish upgrade Deployment cards list the word "Attachment" above their abilities. These cards can be
attached to other Deployment cards as follows:

· When deploying units during skirmish setup, if a player has one or more "Attachment" cards included in his
army, he places each of these cards on one of his non-upgrade Deployment cards.

· Each Deployment card can have only one "Attachment."

· Abilities on "Attachment" cards apply to all figures in the corresponding group.

· Many attachments require the group to have a specific trait, such as "TROOPER." Attachments with these
restrictions cannot be placed on a group that does not have the trait.

When the last figure of a group with an "Attachment" card is defeated, the opposing player scores VPs equal to
the deployment cost of the "Attachment" card in addition to the VPs scored from the defeated figure.

(TL;DR: Yes.)