There is a long discussion in the Cambridge Grammar of the English Language (p1441-1443) of the typical contexts in which the get-passive is more likely than the be-passive. The CGEL notes that:
i Get-passives tend to be avoided in formal style,
ii Get-passives are found only with dynamic verbs,
iii Get-passives are more conducive to an agentive interpretation of
iv Get-passives are characteristically used in clauses involving
adversity or benefit.
Following are various extracts from CGEL's discussion of points ii-iv. (The authors do not regard point i as in need of further comment.)
The restriction to dynamic verbs: be is not replaceable by get
in examples such as:
It got believed that the letter was a forgery.
Obviously, the manager gets feared by most of the staff.
Agentivity: Take for example the pair Jill was/got arrested. Either
could be used used to report an event where Jill simply had a patient
role, but if I believe she set out to provoke the police into
arresting her or was careless in letting it happen I will be more
likely to use the get version.
Adversity and benefit: Get occurs predominantly in passives
representing situations that have an adverse or a beneficial effect on
the subject referent, or on someone associated with it, rather than in
passives representing purely neutral situations. Typical examples: Kim got sacked. My watch got stolen.
Such examples are much more natural than, say, The milk got bought at
the store down the road or The door got opened by a shabbily dressed
Swan, in his pedagogic grammar, Practical English Usage (p223) notes a further difference:
The get-passive is not often used to talk about longer, more deliberate planned actions:
?Our house got built in 1827.
?Parliament got opened on Thursday.
Finally, the Cambridge Grammar of English (a different text to the CGEL) observes (p539):
Prepositional phrases expressing an agent, although they do occur
with get-passives, are far rarer than with be-passives.
In other words, She got arrested by the Austrian police is less likely than She was arrested by the Austrian police.