According to the documentation Xrm.Navigation.navigateTo method doesn’t have any option to open bulk editing but investigating the code I found the way to do that.

Here is an example of the code that could be used to open Bulk Editing:

Xrm.Navigation.navigateTo({
	pageType: "bulkedit",
	entityName: "contact",
	entityIds: ["85dadf2d-0ffd-ea11-a815-000d3a33b4ee", "d7a0d20d-0df9-ea11-a815-000d3a33b4ee"],
	formId: "fd140aaf-4df4-11dd-bd17-0019b9312238"//this parameter is optional
}, {
	target: 2,
	width: {
		value: 80,
		unit: "%"
	},
	height: {
		value: 80,
		unit: "%"
	}
});

Key points here are passing “bulkedit” value to pageType, schema name of the entity you want to open for bulk editing to entityName and an array of ids of records to edit to entityIds parameter. Parameter formId is optional but if you want to use a specific form it’s the way to pre-set it.

And this is approach is not documented so unsupported so use it wisely.