Yah its a good idea!

but it should not be so easy
firstly, You should search the prison key, How? type /c !findkey
pm>> Hurry before a cop arrives
all the cops get alerted, the guy should remain in VCPD hq by the time you find the key
after 60 seconds, pm>> you have found the key
or pm>> The key is with the sergeant who is having vacations in San Andreas, Jailbreak failed

then type /c !jailbreak <nick/id>
the prisoner gets pm>> You have been busted out!
we can have a 50-50 probability for finding the prison key