When do I use Present Continuous for near future instead of "be going to"?

Solution 1:

The present continuous used for the future implies planning and arrangement:

There is a suggestion that more than one person is aware of the event, and that some preparation has already happened. e.g.

edufind.com

I'm meeting Joe at the station > implies > Joe and I have arranged it.
I am arriving tomorrow. > implies > I have my ticket.
We're having a staff meeting next Monday. > implies > The staff knows about it.

Another instructor adds intention as an implication, and wisely recommends mentioning the future time frame to avoid ambiguity:

We use the present continuous tense to talk about the future when an action or situation is part of a (sic):

plan
an arrangement
intention.

Mary’s studying in the library. (now)
She’s studying at Bethan’s house this evening. (future)

Learnenglishlanguagewell.com

The notion of near future will be impacted by the intensity of the intention, planning and arrangements.

• We are meeting next week.
• He is graduating next May.
• I am retiring in six years!