"had been brought back" is Past perfect tense. mean that it happened in the past and is still happening a little bit more at the time of present ,not finished yet.I mean that: They are seeing their car
example : Past simple . happened in the past and finished at the time it happened
They immediately (2)__phoned_
they (4)__returned
"was parked" is a Simple past tense . I think that also can use " parked"
ex: Active - Ann wrote a letter or They offered Ann the job
Passive - A letter was written by Ann or Ann was offered the job
or The job was offered to Ann
All these things I say above is just my little experiance about grammar , I am not really sure that its right 100%, because i learned about it for long time ago .But i have tried my best to help u , hope that it will be help you understand what i want to say .
By the way , "it is understood and
Could you please explain it to me?" should say "it is understanding....parked also like ...., isnt it? " and " Could you explain it for me , please " . I think , with this my sound is better then yours

best wishes