The age of the source particles is part of the payload. Use this check box to specify that the recipient inherits the normalized age of the source.
However, this doesn't seem to work very well with tapes. I'm still checking it, maybe there is a better way.
So here's a workaround.
Copy this into a module script
This reads the Normalized Age source particles so we can use them later.
Add the module in the particle update after the particle status, but before all other update scripts (at least before all scripts that should be affected by your source particle).
Now you can use a color module and use Particles.SourceParticleAge to animate the alpha of the trail.
Hopefully that helps!