Ruling on not praying in congregation in order to catch the company bus
Question

We leave work after Maghrib prayer in a bus belonging to the company, and the adhan for `Isha’ is given when we are still on the bus. There are mosques along the way, so do we have to get off the bus to offer the prayer in congregation? Please note that the bus will not wait for us; rather it will continue on its way, so we would have to wait for other means of transportation to return home. Please note also that the time of prayer does not end when we arrive home on the bus; rather the time for praying in congregation has ended. Is praying in congregation obligatory in this case, so must we get off the bus, or can we continue our journey and offer the prayer individually at home?
Praise be to Allah.Firstly: It is prohibited to delay the prayer until the time for it has ended
It is obligatory to offer the prayers on time , and it is prohibited to delay them until the time for them has ended, except for one who intends to put prayers together when there is a concession allowing him to do that.
Allah, may He be exalted, says (interpretation of the meaning):
{Prayer is prescribed for the believers at specific times}
[an-Nisa’ 4:103]
{Maintain with care the [obligatory] prayers and [in particular] the middle prayer and stand before Allah , devoutly obedient}
[al-Baqarah 2:238]
{But after them came generations who neglected prayer and pursued their desires. So they will meet with perdition}
[Maryam 19:59].
Ibn Mas`ud said regarding al-ghayy (translated here as perdition): It is a valley in Hell, that is very deep and has a foul taste.
The Prophet (blessings and peace of Allah be upon him) said: “Do not associate anything with Allah, even if you are cut into pieces and burned. Do not neglect any prescribed prayer deliberately, for whoever neglects it deliberately no longer has any protection. And do not drink wine, for it is the key to all evil.” Narrated by Ibn Majah 4034; classed as hasan by al-Albani in Sahih Ibn Majah.
If the adhan is given for `Isha’ when you are on the bus – as mentioned in the first part of  your question – you must first pray Maghrib before you get on the bus, or get off the bus to pray on time. Beware of delaying Maghrib prayer or getting on the bus before praying it in the situation mentioned, because the time for Maghrib is very short and the things that may cause delay are many. So you must take precautions in all circumstances and pray Maghrib before you get on the bus, even if you assume that the bus can reach your stop before the adhan for `Isha’, so how about in the case you mention, that the adhan for `Isha’ is given when you are on the bus?
Secondly: valid excuses for not praying in congregation
Praying in congregation in the mosque is obligatory for every adult man who is able to hear the call, according to the correct scholarly view, because of a great deal of evidence which has been explained previously in the answer to question no. 8918.
There are valid excuses which make it permissible not to pray in congregation, one of which is fear for one’s wealth or property.
It says in ar-Rawd an-Nadi Sharh Kafi al-Mubtadi, p. 107: And the one who fears the loss of his wealth, such as grain in storage, or he fears that it may be destroyed or lost, such as if he fears that bread or food will be burnt, or that his mount may wander off, or that his slave may run away, or he fears some harm to his livelihood that he needs, or to property that he was hired to look after, such as looking after a garden, is excused for not praying Jumu`ah and prayers in congregation… End quote.
If getting off the company bus will result in having to pay money to ride on another bus, this is an excuse which makes it permissible not to pray in congregation, but if you can do the prayer in congregation before getting on the bus, you must do that, otherwise you are excused. As for doing the prayer after its time has ended, that is not permissible.
For more information, please see the answer to question no. 212542.
And Allah knows best.