As long as the leads, amp probes, ignition leads use banana plugs to connect to the Snap-on scope, you can use the AES Flexible Adapter -- Male BNC to Banana Sockets (AES# 08-88-M)
to connect them to your Snap-on scope.
The Pico requires each channel to be grounded. Can each of the Snap-on leads make a ground connection at the car?
Snap-on's ignition leads have a unique input impedance, works great with Snap-on scopes, but not as well on other scopes.
For the amp probes, you can create a "custom probe" to accomodate any differences in scaling if Pico's built-in custom probes don't match.