Gated tracks

You'd have to check with local council Darryl, many of HEMAs paper and digital scanned maps of these are out of date.
Sometimes access roads / road reserves get sold by councils, sometimes landowners simply acquire little used routes by fencing or gating illegally.

Personally I feel going through gates isn't wise for 4WDrs to do, it just makes the recreation look bad to locals who may have this land legally, and gives them a good leg up to say in the local scene how bad 4WDrs behave etc.
A 4WDr may have the best intentions, passing through / not camping, drive with consideration to the land, stock etc, but it still looks bad in the landowners eyes, I guess how someone would feel if a stranger parked a car in their front garden and left it their for a few hours / the day.

I find Google Earth is great to assist planning trips / routes.
You can follow map tracks on the sat images, and get a pretty good idea if a tracks turns into a paddock most times.

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Map publishers usually have a disclaimer in some form.

Hema's maps say "Conditions on this map are constantly changing. Whilst every effort has been made to ensure the accuracy of this product, the publisher accepts no responsibility for any errors or omissions which may be contained herein."

I would be very apprehensive about passing through a gate unless it was on a recognised public access road or track. The absence of a "trespass" or any other sign is no assurance of legal access.

Yes, I agree with Les and Allan.
That said it's not unknown in Vic for locals to take down official road signs cos they don't want other people using 'their' roads or tracks.
Best to do your research first. In Vic a recent Rooftop or Vicmap topo is a much better guide to gates and seasonal closures than Hema.

I came across this scenario last year where the land holder placed gates on his land but had no right to restrict thru traffic, as the track was public. Where the problem also arises is when the land is sold (from leasehold to freehold) and an update to maps is not done, either by the mapping company, or the relevant info past onto these companies by the new landholder. I my opinion, when I am in doubt, I try and find the homestead and explain what I wish to do. Most times this is not a problem in getting permission, and in fact, the land holder will give me good advice on where to travel and what to see as I travel through is property.

"If a track is marked on a map (without any warnings or restrictions marked) can it be legally used."

In Victoria, whether or not a road or track is marked on a map - even the official state government produced maps like the VicMap / SpatialVision maps - means nothing as regards to whether it is legally open to the public or not.