Frankly Losar celebration is more politically motivated to cozy up to China and to spite at the Indians. Its hardly about cultural affinity.
Although Tibet is occupied by China culturally China is several hundreds of miles away from Nepal on the other side of Tibet.
"Nepal is traditionally in the chinese sphere of influence."
LOL. You are saying it out of your antipathy for Indians. I doubt you really believe that yourself. The fact that Nepal even exists is because of India.
losar is the tibetan new year which preceeds Buddhism by over a 1000 years and it is a major holiday. There is also the newari new year which is a much younger calendar and is celebrated in only Kathamndu and called Nepal Sambat. In nepal there are 4 major new years.
The Gergorian one, Bikram sambat (what carrot and stick called nava barsa which just means new year), The chinese one, and Nepal Sambat. All 4 are referred to as nava/naya barsa
The entire top 2/3 of the country is of at least some tibetan descent the indian descent ones are the lower 1/3 in the Terai flat lands and look distinctly different. In the terai region they speak maithali which is almost identical to Hindi. The terai was actually given or given back depending on how you look at it, to nepal by the British Raj so at one point it was part of india.
Tell a newar or a tibetan they are of indian descent and you will get quite a few laughs. There are a ton of castes in the country the majority of the country is very different from india and i have been to both places.