Environment probe and other special texture in Material file

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I'm currently writing a test using PBR shader.
Right now it works, but I'm using pre-calculated environment (irradiance) map.

I know that an environment is provided with the deferred rendering, but I want to use the texture sampler in the main shader because the calculation for the sampling (importance) is different.

I would like to know if it is possible to access the sampler (to be bound) when during the 1st pass of the deferred. (for example texture15).

Thanks;