Can I cut side window glass?

No sir they are not. Safety glass is the glass the windshield is made from. Two layers of glass with a thin layer of plastic on between. That is safety glass. It's made to break as non violently as possible so that most of the broken glass sticks to the laminate between the two sheets of glass. It also helps keep occupants inside the car by giving instead of just shattering. Safety glass and tempered glass are two completely different things. But Safety glass CAN certainly be cut. We've had it done before where I work. Since no one makes custom curved glass, when we chop a top, we have to choose a glass that is close to the curve we will end up with and cut it to fit. Matt's had it done a lot. We use Billy's Mobile Glass out of Macon.
Saftey glass is not made to break non violently. It's shards are way more lethal than tempered glass. The safety comes from the layer in between the two layers as you described. Broken tempered glass is WAY less dangerous than Safety glass. Thats why they used tempered glass in doors and close to the floor windows. It turns into 50 million harmless shards.