From The Long Guide by Frankelstner:
Heists usually have a chance of about 10% to 25% to have an escape
level if alarm went off (if the heist does support escapes at all).
Every dead civilian adds 5% to this chance. The expert driver asset
removes the chance entirely. If there are several possible escapes, they
are all equally likely to occur.
The levels usually enable escapes immediately when the alarm goes off.
Once all players enter the escape zone (2 seconds before the level
actually finishes), the game checks if escapes are enabled at all and
if they are, the escape chance is evaluated. If alarm goes off after
all players have entered the escape zone, the stealth bonus is lost,
but there will not be an escape. Day 1 of Framing Frame and day 2 of
Rats enable escapes only after a delay: There is no escape as long as
all players enter the escape zone before that.
As for the actual escape data:
- Trustee Bank: 15% chance on gold and cash, 5% else. Possible escapes: Cafe, Park, Street
- Jewelry Store: 25%/27%/32%/36% chance on N/H/VH/OK+DW difficulty. Possible escapes: Cafe, Park, Street
- Ukrainian Job: 30%/33%/35%/37% chance on N/H/VH/OK+DW difficulty. Possible escapes: Cafe, Park, Street
- Four Stores: 30% chance. Possible escapes: Cafe, Park, Street
- Diamond Store: 10% chance. Possible escapes: Cafe, Park, Street
- Framing Frame day 1: 25% chance. Possible escapes: Cafe, Park. Escape chance enabled 25 seconds after the alarm.
- Framing Frame day 2: 24% chance. Possible escapes: Overpass, Park
- Nightclub: 25% chance (killing civilians has no effect). Possible escapes: Cafe, Garage, Overpass, Park
- Rats day 1: 45% chance when lab not exploded, else 100%. Possible escapes: Garage, Overpass. The chance is actually 25%, but the 4 cooks killed at the beginning count as civilians.
- Rats day 2: 25% chance, enabled once police arrives (80 or 90 seconds after the alarm if no police ambush, else 0 seconds). Possible
escapes: Overpass, Garage (if there was an escape on day 1, choose the
- Transport Harbor: 15% chance. Possible escapes: Garage, Overpass
- Transport Crossroads: 15% chance. Possible escapes: Cafe, Street
- Transport Park: 15% chance (killing civilians has no effect). Possible escapes: Cafe, Overpass, Street
- Transport Downtown: 10% chance. Possible escapes: Cafe, Park
- Transport Underpass: 10% chance. Possible escapes: Park, Street
Notes on the escapes:
- Overpass: Bain announces at the start whether to expect a van or helicopter. There is only one possible van location, at the parking
- Garage: After going up the staircase, stick to the left and jump over the barrier. Hug the wall and cross over to the other side. After
a few more turns to the left there will be a door to the left. Open it
and you are at the van.
- Park: The van only arrives in streets which are not blocked by police vehicles.
- Cafe: The map has three possible van locations, but the location closest to your spawn is disabled.
To add to this, contrary to popular belief, leaving during or after an assault does not affect the chances of getting an escape mission.