In the name of Allah, the most Beneficent, the most Merciful.
The watn asli usually refers to a persons hometown where he has taken up residence or a place besides his birthplace in which he has assumed permanent residence along with his family. After settling he has no intention of leaving the place. (Bahrur Raaiq p.136 v.2)
If a person relocates with his family and possessions to his place of employment with the intention that he will live there forever even if his employment terminates then this place will assume the status of watn asli. However if a person relocates with his family but intends to live in his place of employment only for the duration of his employment then there are two opinions. Some scholars say this place will not be regarded as his watn asli. Where as other scholars have regarded such a place as watn asli, i.e. both places will be considered as watn asli. (Ahsanul Fatawa p.102 v.4)
Ibn Humam (RA) in his Fathul Qadeer has written that a place will cease to be regarded as watn asli if the following two conditions are found:
- A person completely disassociates himself from his watn asli and moves away with his family.
- He assumes permanent residence in another town.
With regards to your question if you have severed all ties with the previous place (not leaving any property or family behind) then if you pass by the previous place on journey you will have to perform qasr salah if you do not stay for fifteen days or more. (Kifayatul Mufti p.350 v.3) However if you intend to live in this place of employment only for the duration of your employment then both places will be your watn asli. (Imdadul Fatawa p.585 v.1) From the question it seems as though both places will be your want asli as you have not severed ties with city A.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.