From the ANO
"By day an aircraft fitted with an anti-collision light shall display such a light in flight"
"display when stationary on the apron by day or night
with engines running a red anti-collision light, if fitted"
No mention as far as I can see of High Intensity Strobe Lights which are not the same as anti-collision lights. Note the words if fitted, hence the use of Nav lights to indicate either engines running or a signal to ground crew that start is imminent.