Yorkshire Dave
Western Thunderer
I've always thought that the plastic webbing just gets in the way, so I normally remove it prior to track painting and ballasting. It's not a job you can really do prior to gluing the track down, though, as the webbing is pretty much essential for maintaining the sleeper spacing etc.
In the past I've painted the track before removing the sleeper webbing. This helps prevent the sleepers moving around whilst cutting the webbing.