Is it permissible for my husband to take lost items of little value from the train workshop if their owners have not inquired about them?

Your husband is not permitted to take what people leave behind on the train forgetfully, except for trivial items, even if officials permit him, because it is a lost item (luqata) and does not belong to them. "Trivial" is determined by custom and common practice. So, anything that is insignificant and not sought after by common people is considered trivial, and it is permissible to take it.