Really not sure what you are trying to say here. First of all the trees are the problem and since the trees are in someones property Openserve can't cut them down and even if they wanted to but the owner refused then it would be the same. The wire running through the trees are not an issue. If the tree falls over and snaps the line it's Openserves problem.
They don't use a support wire for tension instead uses like coiled up fence wire (not wire stole from a fence just similar) to warp around the fibre to hold it. You will be surprised how strong those very thick fibre wires are as they hold the strands for quite a few households.
When they install the fibre line like in your last picture (so looks like you guys already have fibre install) they loop a few loops in case of a break and then suspend the fibre in the same manner they use from pole to pole to the high point on your property. They don't use any support wire as that would probably expand and contract more than the plastic shield around the fibre. It doesn't make it shoddy workmanship though.
Also contact with any ISP.... Well if you looking at contracts you are doing it wrong. Go with month to month ISP's like Cool Ideas, Afrihost, Axxess,RSAWeb and others. All the ISPs are month to month to month if you pay your own installation and if not then you usually just pay the installation fee back pro rata.
If the tree falls over and snaps the fibre it would probably be an extended outage to which your ISP will probably log a fault then Openserve will suspend billing until the fibre break can be fixed. They won't rip you monthly if you don't have service.
Ohh and if you look nicely the low hanging wire is the old copper lines. Those will probably come off when everyone is eventually shifted to fibre and adsl is gone and considering how long those copper wires have been hanging like that I don't think you should be worried about the new fibre lines installed.
