Video:

Formally, it's enough to start the mission while on taxi mission with passanger in cab. However, unfortunately game crashes if some special models (like Joey's) are not loaded. Guaranteed way to avoid crash is to start Salvatore's Called A Meeting and end it and then immediately instapass (like shown in the video, mission is aborted by firefighter). If I remember correctly, it was tested that starting Dead Skunk In the Trunk after attempting and failing mission doesn't lead to a crash of instapass. However, trying this instapass without starting mission first with current any% route leads to a crash.

Edit: you don't actually require a passanger, you can keep caps without picking one up.

So since nobody has posted it here before and I was testing anyway... you can do Patriot Playground instapass and immediately after that Salvatore's Called a Meeting instapass without crashing, but I have no idea yet if there will be a good lineup of rampages used in an All Missions or 100% run for this to be useful.