Hello, I can´t find this one in my grammar books or online either, I found an abstract of an academic paper saying it was a ´sharper´ version of -mİs olmak but don´t know what that form means either. here are two examples, sorry they are near paragraph-length sentences

Biz İstanbul Sarıyer Gümüşdere halkı olarak Tarım alanlarımız üzerine İSKİ tarafından yapılması düşünülen arıtma tesis projesini bu bölgeden kaldırılması için bir senedir verdiğimiz mücadeleyi kazandığımız sırada arazinin özelleştirmeye açıldığını öğrenmiş bulunuyoruz.

Betonların gıda olarak tüketilemeyeceği gerçeğinden yola çıkarak, bu bölgede ekolojik  dengeyi sağlamak, İstanbulumuz da çok az kalan tarım  topraklarına, ağaçlarımıza, evcil hayvanlarımıza, bölgeyi yurt edinmiş yaban hayvanlara ve yatırımlarımıza sahip çıkmak için el birliği, iş birliği ve gönül birliği yapmış bulunuyoruz.

my best attempt at translation (I found the first sentence extremely difficult):

We, the people of İstanbul Sarıyer Gümüşdere, have given a year to and won the struggle for the cancellation of the treatment plant project (a project thought to be the doing of İSKİ on farmland in this region, but have learnt land is in line for opening up to privatisation.

Considering that concrete cannot be consumed as food, for this region to provide the ecological balance, in order to protect our İstanbul´s very little surviving farmland, our trees, our pets, the wild animals who use the area as habitat, to protect our investments we have made a union of hands, of works and of hearts.

i.e. seemed something like an english ´perfect´ aspect would possibly fit?

emoticon was accidental btw

- mış bulunmak form can be used for to make a stylish and formal statements.

Bugün Türkçe öğrenmeye başlamış bulunuyorsunuz.

Today, you started to learn Turkish.

Böylece dersin sonuna gelmiş bulunuyoruz.

We, now came to the end of the lesson.

Should the we/ us personal pronoun ´-uz´ always and only be attatched to ´bulunmak´ in this case?

No. You can use also other personal endings with this form.

Exp :

http://www.gundem.be/tr/belcika/buyukelci-m-hakan-olcay-gorevime-baslamis-bulunuyorum

"yap-mak" and "yap-mış bulunmak" are almost same and can be used for each other.

the slight difference is "-mış bulunmak" sounds more formal. and in most cases "-mış bulunmak" is used for actions done by unwillingly. or whether you like it or not, its cause isnt your direct intention, you have to do sth and you did it.