1. Police cannot interfere in civil matters. However if there is any likelihood of physical violence when your grandmother visits the land in dispute, then you can seek the help of Police Department.
2. Since it is a civil matter Police may reject the complaint. But the complainant has to apprise the Police of the likelihood of violence which may breakout during your grandmother's visit to the disputed land.
3. Your mother can approach the civil court against her siblings for declaration, partition and separate possession of her share in the property provided your grand parents have died intestate (without executing a WILL).
4. A property is said to be a self acquired property, if the property is earned by the individual out of his own funds he should have acquired whereas a property is said to be ancestral of a paternal one from great grandfather to great grandchildren and has traversed for 4 generations without any partition.
5. There has to be record of your grandfather's investments to prove that one of your uncles' had indeed acquired farm land out of your grandfather's investments.
6. There are sufficient grounds for your mother to stake claim on the property as she has equal share along with her siblings.
7. Documents required are Family Tree, Land documents, Katha certificate, etc.