"Get" + "married" can be either an adjectival passive or a verbal one:
In the former, "married" is an adjective; in the latter a past participle verb.
 They are hoping to get married by the bishop. (verbal passive)
 They are getting married at the weekend. (adjectival)
In  the by phrase makes it clearly verbal, so "married" is a verb here. In  there is no explicit or implicit agent, and even though "married" (unlike "engaged"), cannot combine with "become" (*“They became married”), "married" is still an adjective here with a meaning similar to "They are marrying each other".
 They got engaged last month.
"Get" + "engaged" is always an adjectival passive. "Engaged" is morphologically related to the past participle verb, but its meaning has changed so it is no longer comparable to a verbal passive. Further evidence of adjectivehood comes from the fact that it can combine with “become”, as in “They became engaged last month”. Only adjectives can combine with “become”.