There is clearly no need for an Engineer to meet the aircraft and do the pushback.
As i understand it,the system employed by for example Jetstar,they have Engineers available if the Pilot requests, as GG pointed out.
I believe in Melbourne for example, these Engineers, 3-4 per shift, reside in an office under the concourse.
Obviously there is a cost saving by not having enough engineers to meet and dispatch every flight.
And when there is an issue, the Aircraft is serviced by a fully licensed Engineer, and signed off.
What i dont understand, is why in between calls as required, these highly skilled Engineers, are not out of the office, and on the ramp doing walk rounds when they can subject to work load?
Surely their eyes and skills should be used when available?