BTA26 has TO3P package with 5.5 mm pin distance, this doesn't basically change the problem. It will help you at least to provide the required clearance without conformal coating or milled PCB slots.
Imagine the track end segment as a triangle with a corner at the pin rather than a round pin of full track width.
If you have wide tracks or copper pours on a power PCB, the thermal calculation will end up in determining point-to-point resistances, acceptable voltage drops and overall power dissipation. The risk of local overheating must be still kept in mind, but considering the lateral thermal conductivity of the copper structures.
An additional comment on the said solder coverage. I know that it's used in some circuits, e.g. SMPS. In my understanding, it will be utilized to reduce the track overtemperature and total power dissipation below permitted maximum values. But it's no reliable method if the copper structures don't have sufficient current capacity, e.g. because you can't guarantee a certain solder layer thickness.
BTA26 rated current is 25A, not 40A by the way.