Few things to know here. ICF coaches are mainly of 2 types. Self-Generating and Non Self-generating.
1. All the normal blue ICF rakes used on normal SF/express/passenger trains ( except some exceptions) are self-generating. They don't need EOGs and each generates it's own power ( A big boon for IR in terms of handling rakes and enabling slip trains). However, one main disadvantage of these coaches, apart from less efficiency and higher maintenance requirements, is that the MPS is restricted. These rakes cannot handle higher speeds as the oscillations can damage the connection between the wheels and the alternator that generates the power.
2....
more... To tackle the above disadvantage, when RAJ and Shatabdi class of trains were started, IR removed the self-generating equipment from the normal ICF coaches and provided them with EOG cars instead. Now the rakes could travel faster. Usually these rakes are rated for 130kmph service, but with appropriate operational clearance there have been instances where these rakes hit 150 Kmph during regular operations. When the Duronto concept was started, ICF built a few non self-generating rakes with duronto livery to be used on these trains.
Coming to your question, the Gujarat mail uses normal ICF Self-generating coaches and thus does not need EOG cars. From what I see in the gallery for Nanda Devi express, it seems to be using an old Rajdhani rake, which as I explained above, needs an EOG car. Similarly, the Howrah-Digha AC Duronto also has an ICF duronto rake which will also need an EOG.