This is a base grounded oscillator.Feedback is provided by parasitic capacitance of C-E junction.
But 1uH choke inductor which is used at collector has very high value. Because at those frequencies the inductor will show capacitive reactance beyond its resonance frequency.
To be more precise the Negative Resistance Oscillator (or negative-conductance whatever you want to be, gain or loss) could be seen as a Colpitts oscillator, with internal transistor base-to-emitter capacitance, and collector-to-emitter capacitance acting as a voltage divider.
This is the reason in this kind of oscillators can be used only transistors with relative high internal capacitances.