In the TNG episode Manhunt, we see that Lwaxana Troi can't read the mind of a hologram (as there is no mind there to read!), but her telepathic abilities are well-renowned. Hence, could she possibly read Data's thoughts? If so, would she read thoughts like those of a human, or would they be lines of code?
No. We see in the Star Trek: The Next Generation Season 3. Episode 20 "Tin Man" that even the most powerful of Betazoids, Tam Elbrun, cannot read Data. Hence it would be extremely unlikely that Lwaxana would be able to read Data.
From the Wiki site:
"En route, Elbrun finds it impossible to filter out the thoughts of the Enterprise crew, but when meeting Data, he is puzzled by finding what he calls 'absence of mind', but also finds relief in developing a friendship with Data, who, being an artificial lifeform, has no thoughts to be read."
Not normally, but once he has the emotion chip it's uncertain.
From TNG 7x01, Descent, Part II:
Deanna Troi: Data, I can sense feelings in you.
Data: Yes. My brother has made that possible.
This means that despite their robotic nature, when Soong-type androids feel emotions it can be sensed by a half-Betazoid - the same as with regular biological beings.
The basis of Betazoid mind-reading is empathetic reading, "feeling" another person's thinking, and is a purely biological empathy, sensing the psychic "expression" in the same way that we might "read" a person's expression and body language. On that basis, an AI life-form, having no psychic presence, would be therefore unreadable, regardless of any sophisticated emotion chips (which are, afterall, just a simulation).