Is it permissible to purchase land via an installment plan from a real estate company, then obtain real estate financing from an Islamic bank to pay its price in cash?

If you are one of the partners in land ownership, it is permissible for the bank to purchase the shares of the other partners and then sell them to you on a Murabaha basis, and this is the safest option.

If it is necessary for the bank to purchase the entire land, then either you pay an advance payment equal to your share of the land, or the bank purchases the entire land and sells it to you on a Murabaha basis, provided that your share does not exceed half (more cautiously: not exceeding one-third), to avoid falling into usury or circumventing it.