Is there alternative way to access session details in deferred custom action?

This must be helpful. Pay special attention to the bottom of the page, a guideline of 2 steps how to pass values via CustomActionData.

Here is the excerpt:

To write the value of a property into the installation script for use
during a deferred execution custom action:

1. Insert a small custom action into the installation sequence that sets the property of interest to a property having the same name as
   the deferred execution custom action. For example, if the primary key
   for the deferred execution custom action is “MyAction” set a property
   named “MyAction” to the property X which you need to retrieve. You
   must set the “MyAction” property in the installation sequence before
   the “MyAction” custom action. Although any type of custom action can
   set the context data, the simplest method is to use a property
   assignment custom action (for example Custom Action Type 51).
2. At the time when the installation sequence is processed, the installer will write the value of property X into the execution script
   as the value of the property CustomActionData.