I'm not sure what other forum members will suggest, but that space is simply too congested for most trees. At best, you could consider something extremely columnar, like a 'DeGroot's Spire' arborvitae or a 'Tiny Towers' Italian cypress. Another possibility would be a dwarf evergreen magnolia ('Little Gem', 'Teddy Bear'), provided you can find one already of some height and with a clear trunk.

Most trees, evergreen or not, that will eventually produce a more spreading canopy (which it seems like you are looking for) will cause all sorts of traffic/headroom issues until they grow up tall enough to walk under/pass by easily. And you just do not have enough room there to plant anything that has already got that kind of clearance.

Do you have room to plant on the outside of the gate?

I can't plant outside the gate as it's HOA grounds. Also there is an existing oleander hedge there.

I am considering Camellia sasanqua or Camellia japonica (but it may get too much sun here) or a bay laurel, standard form. Any comments on these?

You will almost certainly end up having issues with anything you plant in such a tight space. I.E. restriction of growth issues. There probably isn't anything that will quickly grow and do what you want it to do, but then just "stop" right there. Either it will grow incredibly slowly and prevent you from reaching your goal for many years, or it will overgrow its space. Contrary to popular belief, trees don't just grow to a certain size and then magically "stop".

If you want something with minimal maintenance... put in a taller fence.

Bay laurel (Laurus nobilis)? Really?

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As stated above......trees just don't stop growing. Sure you could prune to limit size of the top growth but who wants to be tied to all that frequent maintenance? To say nothing of how the roots will react under that sort of hardescape confinement.

You'd need an extremely narrow plant. Perhaps a Sugar Maple like Newton Sentry since they are somewhat shade tolerant.

Sorry if I missed some details just wanted to throw out a quick suggestion.

In Palo Alto California?

Yes, really. Bay laurels rarely get as large as the one shown above from Wikipedia - I'm not even convinced that that is Bay laurel and not California laurel. They are very slow growing, that tree above must be at least 50 years old if it really is a bay laurel/sweet bay. Bay laurel tends to be more of a shrub left alone.

"FDR96 Sweet Bay Laurel ( Laurus nobilis )
Bay laurel is a pyramid-shaped tree or large shrub with aromatic, evergreen leaves and shiny gray bark. It can reach 60' in height in its native range, but generally is much smaller (3-10' tall) in culture. "
http://www.seedman.com/trees/laurus_nobilis.htm

Here are some more typical specimens, they are very easy to prune and shape - I already have 2 little topiary bay laurels in urns.

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and as a shrub

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I decided - and planted! Manzanita Dr Hurd... it's only 18" tall now so it will be a long time before it resembles a tree, but I can't believe I didn't think of manzanita before - or have it suggested. It should reach around 10' at maturity and has an upright growth habit. Beautiful branches and evergreen foliage.

Arbutus unedo might have worked.

Instead of a tree (there's no room), put a lattice on top of the wall, and train vines along it.